Unit 5 Period 4 Developing ideas-【金版教程】2024-2025学年高中英语选择性必修第四册作业与测评课件PPT（外研版2019）

WELCOME UNIT Unit 5　Into the unknown Period 4　Developing ideas 　 课时作业(四) 课时作业(五) 目录 CONTENTS 1 2 课时作业(四) Ⅰ　根据语境及汉语提示完成句子 1．He was amazed at all the colourful _____ (珊瑚) reefs, and all the beautiful fish. 2．The system can print electronic features smaller than a hundredth of a ___________(毫米) wide from a variety of materials. 3．I don't want to go there, ___________ (此外), I have no time to do so. 4．Between the man I had been and that which I now became there was a very ________ (显要的) difference. 5．We can distinguish one kind of __________ (物质) from another by its features. coral [基础训练] millimetre furthermore notable substance 课时作业(四) 4 Ⅱ　单句语法填空 1．Changing his job like that is equivalent ____ giving him the sack. 2．Recently, more and more _____________ (archaeology) discoveries have been made along the Silk Road. 3．The course in philosophy opened ____ new horizons for the students. 4．People formed an orderly queue as they waited ___________ (serve). 5．The dangers of _______ (drill) and transportation in the Arctic are great. to archaeological up to be served drilling 课时作业(四) 5 Ⅲ　单句写作 1．许多因素可以导致胎儿发育迟缓。 Many factors can _______ growth retardation in unborn babies. 2．这种设计后来被称为东方风格。 This design came to be __________ the Oriental style. 3．这些实验的目的就是探索这两种现象之间的联系，如果存在着任何联系的话。 The object of these experiments was to find the connection, ______， between the two phenomena. lead to known as if any 课时作业(四) 6 4．许多人认为获得财富等于取得成功。 Many people believe that being wealthy ______________ gaining success. 5．海平面正在以每年2毫米的速度提升。 Sea levels are rising _____________ almost 2mm a year. is equivalent to at the rate of 课时作业(四) 7 Ⅰ　阅读 A At 2：30 on December 5，1945, five US Navy training planes took off in clear weather from the base Lauderdale, Florida. The planes flew cast over the coast ... and disappeared. The group was Flight 19, on a run between Florida and Bahamas. Tailor was the group leader. At about 3：40, Tailor reported that his compasses were not reading properly. The other planes followed their leaders aimlessly, first east, then west, then northeast over the ocean, as Tailor tried to make sure of the direction by radio. Then, suddenly Tailor was heard to give orders to dive ... [思维训练] 课时作业(四) 8 Quickly, two giant Martin seaplanes were sent up to search for Flight 19. Several hours later, the wind became strong and visibility (能见度) dropped. A return to base was ordered. But only one of the Martin seaplanes landed. Four days later, the Navy and Coast Guard combed a 100，000 square miles area with more than 100 planes and ships. No sign was ever shown of the missing planes. Today, people have noted the disappearance of many ships and planes in the southwest part of the North Atlantic and began to call this area the Bermuda Triangle (百慕大三角区)． 课时作业(四) 9 The points of the triangle are Bermuda, Puerto Rico and a spot in the Gulf of Mexico, west of Florida. It is a two-faced water world of tiny islands, bright beaches and beautiful waters. Yet thick fogs, powerful currents (激流) and sudden storms are hidden behind this smiling surface. 篇章导读：本文是一篇记叙文。文章主要讲述百慕大三角洲的飞机消失的神秘事件。 课时作业(四) 10 1．Why did Flight 19 disappear? A．Because the wind became strong and visibility dropped. B．Because Tailor was given wrong orders to dive. C．Because Tailor couldn't read his compasses correctly. D．Because something unknown made the compasses unable to work as usual. 答案：D　推理判断题。根据第一段倒数第三句“At about 3：40, Tailor reported that his compasses were not reading properly.”可推知，美国19飞行队消失是因为一些未知的东西使得指南针不能像往常一样转动。故选D。 课时作业(四) 11 2．In what position did Flight 19 disappear? A．In the southwest part of the North Atlantic Ocean. B．In the northeast part of the North Atlantic Ocean. C．To the southwest part of Bermuda in the Atlantic Ocean. D．To the northeast part of Bermuda in the Atlantic Ocean. 答案：A　细节理解题。根据第三段可知，今天我们已经记录了很多船只和飞机在北大西洋西南部的百慕大三角区失踪。因此美国19飞行队消失在北大西洋的西南部分。故选A。 课时作业(四) 12 3．How many planes disappeared altogether that day? A．Five. B．Six. C．Two. D．Only one. 答案：B　细节理解题。根据第一段第一句的“five US Navy training planes”以及第二段第一句“Quickly, two giant Martin seaplanes were sent up to search for Flight 19.”和第四句“But only one of the Martin seaplanes landed.”可知，那天有六架飞机消失。故选B。 课时作业(四) 13 4．The underlined word “combed” in the passage mean “________”． A．covered with B．flew over C．did up one's hair with a comb D．searched all over 答案：D　词义猜测题。根据第一段内容可知， 5架飞机消失；再根据第二段第一句和第四句可知，后来派出去的两架水上飞机仅有一架返回，因此四天后，海军和海岸警卫队使用100多架飞机搜索了10万平方英里地方。因此推断comb的意思与D项意义相近。故选D。 课时作业(四) 14 B One day John was looking out of the window when he saw a huge blast of light, followed by an extremely loud explosion. He looked up and saw a huge cloud of dust surrounding the moon. When the dust settled, John saw the strangest thing—the moon was almost split in half. John's mom ran over to see what had happened. Then John and his mom heard a couple of men speaking out loud through the open window. “I told you there were aliens (外星人) out there！” one man exclaimed loudly. 课时作业(四) 15 “You have to be out of your mind! Our astronauts would have found that out, if that was true，” the other man replied. “Wow, an alien invasion！” John cried excitedly. “Calm down, John. There has to be a more believable story than the alien nonsense，” his mom said. John and his mom moved away from the window to watch the news, hoping that someone would say something more realistic than the alien story. On the news, some scientists agreed that the split of the moon, was a result of a major moon-quake. On the other hand, the religious people all agreed the moon split was a sign from God that the end of world was near. 课时作业(四) 16 Time passed by, and there was no definite answer as to what exactly had happened to the moon. So, the mystery continued while the moon appeared to be shining brighter than ever. “How do you like my mystery story, Dad？” Adam asked his father. “Great! But I have one question. Don't you think that your ending leaves the readers hanging？” his father asked. “Very true. But that's the beauty of it. Mystery stories are even more exciting when the ending stays a mystery, leaving it to the readers' imaginations to pick the ending they like，” Adam replied. 课时作业(四) 17 篇章导读：本文是一篇记叙文。文章介绍了Adam (亚当)写的荒诞小说——John (约翰)在往窗外看时，发现一阵爆炸声过后月亮被分成了两半。有人认为是外星人入侵；有的认为是上帝想毁灭世界的象征等。但是，究竟是什么原因，没有人能给出确切的答案。 课时作业(四) 18 5．What's the most unbelievable thing for John? A．John was looking out of the window to enjoy the moon. B．John noticed that an extremely loud explosion. C．John found the moon was almost split in half. D．John saw a huge cloud of dust surrounding the moon. 答案：C　细节理解题。根据第一段最后一句“When the dust settled, John saw the strangest thing—the moon was almost split in half.(当尘埃落定，约翰看到了最奇怪的事情——月亮几乎被一分为二。)”可知，对John来说最不可思议的是他发现月亮几乎被分成了两半。故选C。 课时作业(四) 19 6．What's the attitude of John's mother toward the statement about an alien invasion? A．Supportive. B．Negative. C．Optimistic. D．Neutral. 答案：B　推理判断题。根据第五段中的“Calm down, John. There has to be a more believable story than the alien nonsense”可以推出，John的妈妈对外星人入侵是持否定态度的。故选B。 课时作业(四) 20 7．What actually happened to the moon? A．Nobody knows. B．A moon-quake took place. C．The alien attacked the moon. D．The God decided to end the world. 答案：A　细节理解题。根据倒数第四段第一句“Time passed by, and there was no definite answer as to what exactly had happened to the moon.”可知，没有人确切地知道到底发生了什么。故选A。 课时作业(四) 21 8．Who wrote the article? A．John. B．John's mother. C．Adam's father. D．Adam. 答案：D　细节理解题。根据倒数第三段“‘How do you like my mystery story, Dad？’ Adam asked his father.”可知，这篇文章是Adam写的。故选D。 课时作业(四) 22 Ⅱ　七选五 The year 79 AD would have seemed just like any other year in the Roman city of Pompeii. Each day, the streets were filled with the sounds of busy shops and customers enjoying the city's many cafes. __1__ No one gave any thought to Mount Vesuvius, a volcano close to Pompeii. Vesuvius had been inactive for years. The soil in that area was good for agriculture. __2__ But the sleeping mountain was about to wake up ... The eruption when it happened, was unlike anything witnessed before. A huge cloud of hot ash rock rose into the air, covering the surrounding area. 课时作业(四) 23 A young man, watching from a distance, recorded how the thick dark cloud spread everywhere. __3__ They took what they could as they tried to get away from the city. But many were trapped by falling buildings. Suddenly, there was a powerful flow of gas, ash and rock. It moved down Vesuvius at a speed of about 450 kilometres an hour. __4__ The city was covered by up to six metres of ash. Pompeii became a city frozen in time. __5__ Many bodies have been found in the same positions in which they fell. Work continues to uncover the rest of the city—and the ancient stories it has to tell. 课时作业(四) 24 A．Pompeii was left in total darkness. B．The city was rediscovered in the mid-18th century. C．The people of Pompeii had no reason to fear the volcano. D．People bathed and chatted happily in the beautifully built baths. E．He described how people were frightened by the sudden disaster. F．When it reached Pompeii, it immediately killed anyone in its path. G．Smoke, mud, flames and burning stones spewed from the summit of the mountain. 篇章导读：本文是一篇记叙文。文章讲述了在公元79年的意大利庞贝城附近的维苏威火山突然爆发带来的巨大灾难。 课时作业(四) 25 1．D　本段第一句提到“公元79年的罗马庞贝城本该和其他任何一年一样。”设空前一句描述庞贝城日常生活的情景。D项(人们在建造精美的浴池里愉快地沐浴和聊天。)也是描述庞贝城中人们的日常生活，顺承设空前一句的话题。故选D。 2．C　设空前一句“维苏威火山已经停止活动多年了。”说明原因，C项(庞贝人没有理由害怕沉睡的火山。)说明结果，顺承上文的话题。故选C。 3．E　E项(他描述了人们是如何被突如其来的灾难所吓倒的。)与上文“一个年轻人从远处观察着，记录下了浓浓的乌云是如何四处蔓延的。”为承接关系。E项中的“He”指代上一句中的“A young man”。故选E。 课时作业(四) 26 4．F　F项(当它到达庞贝城时，它立刻使流经路上的人都死去。)与上文“它以每小时450公里的速度向维苏威火山移动。”为承接关系。F项中“it”和设空前一句中“It”都是指代“a powerful flow of gas, ash and rock”。故选F。 5．B　B项(这座城市在18世纪中叶被重新发现。)与下文“许多尸体都是在他们倒下的地方被发现的。”为承接关系。B项中“rediscovered”与下文的“have been found”和“uncover”语义相同，是词汇复现。故选B。 课时作业(四) 27 【持续背记】 ①There are a wide range of activities available for all the students to participate in. 有多种活动可供所有学生们参加。 ②Applying the sandwich label to burgers is less controversial, but it's still worth debating. 把汉堡包称为三明治虽然争议没那么大，但是也值得商榷。 ③Going eastward, you'll pass mountains and thousands of lakes and forests, as well as wide rivers and large cities. 向东走，你会经过群山、成千上万的湖泊和森林，还有宽阔的河流和大城市。 课时作业(四) 28 【持续积累】 课时作业(四) 29 课时作业(五) Ⅰ　根据语境及汉语提示完成句子 1．I can see things just going onwards and ________ (向上) for us now. 2．It's a ________ (海沟) that used to be dry, but now has water in it. 3．The clean bottles at the corner are ________ (整齐地堆起) neatly in piles of three. 4．Once ashore, the ______ (舰) was thoroughly inspected by the police. 5．They narrowly escaped __________ (沉船) in a storm in the North Sea. upwards [基础训练] trench stacked vessel shipwreck 课时作业(五) 31 Ⅱ　单句语法填空 1．His new career doesn't pay nearly as well ____ the old one. 2．So, I lost my bike, but ___________ (equivalent), I was given a chance of going abroad. 3．We must take _____ our own hands the determination of our future. 4．I shaved a few __________ (millimetre) from the bottom of the door to make it close properly. 5．Every dog or cat has its own needs, some of _______ are specific to the breed. as equivalently into millimetres which 课时作业(五) 32 Ⅲ　用括号内所给词汇，写出一个语段 (be equivalent to, archaeological, shipwreck, substance, furthermore) ﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍ A recent archaeological research has found a shipwreck at the bottom of the sea. The wreck measures twenty metres in length, which is equivalent to a large room in size. Furthermore, the researchers also found some valuable substances in it. Hopefully, we can get more information about it. 课时作业(五) 33 Ⅰ　七选五 Mind­wandering can help boost our mood Prior research suggests a wandering mind is an unhappy mind: We tend to be less happy when we're not focused on what we're doing. That's likely true. __1__ For example, as one 2013 study showed, when people found their wandering thoughts more interesting, their moods actually improved while mind­wandering. Similarly, other studies have found that thinking about people you love or thinking more about your potential future than about what happened in the past produces positive results. [思维训练] 课时作业(五) 34 How you use mind­wandering may also be important. __2__ It has been mostly unexplored in previous research, but likely has distinct effects. As one 2017 study found, people who use daydreaming for self­reflection typically have more pleasant thoughts than people who simply think about unpleasant experiences. There is even some evidence that mind­wandering may be more of an antidote (缓解方法) to depression than a cause. People who are depressed may simply replay events from their past to better understand what happened to cause their dark mood and avoid future problems. Also, when researchers studied whether a negative mood preceded or allowed a mind­wandering episode, they found poor moods led to more mind­wandering but not vice versa. __3__ 课时作业(五) 35 Now, findings from a 2021 study suggest that mind­wandering that is more freely moving can actually improve your mood. In this study, participants were prompted randomly via cell phone over three days to report how they were feeling and how much their thoughts were freely moving and related to what they were doing. After analyzing the data, the researchers found that when people's thoughts were off­task, they generally felt more negative—similar to what earlier findings showed. __4__ “Our findings suggest there might be positive aspects of mind­wandering，” the researchers conclude. __5__ If I simply put myself in a space that lets my mind move freely, I don't get depressed. On the contrary, I'm happier because of it. 课时作业(五) 36 A．In some cases, people intentionally mind­wander. B．Mind­wandering is part of our human inheritance. C．Again, I find that science supports my own experience. D．There may be a right and a wrong way to mind­wander. E．But if their thoughts were free­moving, it had the opposite effect. F．In fact, the content of wandering thoughts makes a big difference. G．It suggests that mind­wandering may be helping people feel better. 篇章导读：本文是一篇说明文。文章主要介绍了自由的神游可能有助于改善我们的心情。 课时作业(五) 37 1．F　上文“Prior research suggests ... focused on what we're doing.”说明以前的研究表明走神的人们不开心，下文“For example, as one ... while mind­wandering.”提到当人们发现自己的走神更有趣时，他们的情绪实际上在走神时得到了改善。上下文为转折关系，F项(其实，神游想法的内容起很大作用。)与上文是转折关系，下文对这种说法加以解释。故选F。 2．A　下文“As one 2017 study found ... unpleasant experiences.”说明人们通过白日梦自我反思会有更多愉快的想法，A项(在某些情况下，人们会故意神游。)符合语境。故选A。 课时作业(五) 38 3．G　上文“Also, when researchers studied ... but not vice versa.”说明糟糕的情绪会导致走神，走神不会导致糟糕的情绪，反而会让情绪变好，G项(它表明神游可能会帮助人们感觉更好。)是对上文的总结，It指代上文内容。故选G。 4．E　上文“After analyzing the data ... what earlier findings showed.”说明人们在分心时，通常会消极，下文“Our findings suggest there might be positive aspects of mind­wandering”说明神游的积极的一面，E项(但如果他们的思想是自由移动的，那就会产生相反的效果。)与上文是转折关系， E项的opposite effect与下文的positive相呼应。故选E。 课时作业(五) 39 5．C　下文“If I simply ... because of it.”讲述作者自己的体验，思想自由移动时会更快乐，这与上文“Now, findings from a 2021 ... can actually improve your mood.”提到的科学研究是一致的，C项(再一次，我发现科学支持了我自己的经验。)符合语境。故选C。 课时作业(五) 40 Ⅱ　语法填空 Wandering sounds, __1__ (regular) rhythms and a carrier of gentle emotions are the musical language of guqin, a plucked seven string instrument created in ancient China. The earliest piece of guqin in China, __2__ was unearthed in Hubei Province in 2016, __3__ (date) back to the Zhou Dynasty. The body of a guqin is made of lacquered wood and the strings of twisted silk. Unlike its seemingly simple __4__ (appear), making a guqin is extremely __5__ (demand). An outstanding piece can take anywhere from two to several decades to craft. It is a crystallization (结晶) of art and time. 课时作业(五) 41 The tone of a guqin is quiet, ethereal and distant. Vibrations are suppressed to produce an undulating (起伏的) and lasting flavor, __6__ abundant empty notes in between. As the listener fills in the voids in their own minds, a connection is formed between music and man. 课时作业(五) 42 The guqin __7__ (favor) by the literati in ancient China. The most renowned guqin musician was Yu Boya in the Spring and Autumn (770-476 BC) and Warring States (475-221 BC) periods. As he played his guqin in the mountains, a woodcutter named Zhong Ziqi heard the music and understood exactly __8__ Yu wanted to express. This deep understanding formed __9__ strong bond between them, and they became close friends. This is the famous tale behind the guqin masterpiece, Flowing Water, High Mountains. The piece has been passed down through generations and is considered one of the most famous and important __10__ (compose) in Chinese guqin music. 课时作业(五) 43 1．________　2.________　3.________　4.________5．________　 6.________　7.________　8.________9．________　10.________ 篇章导读：本文是一篇说明文。文章介绍了中国古琴的历史、结构以及有关的故事。 课时作业(五) 44 1．irregular　考查反义词。设空处应用形容词作定语，修饰名词rhythms，irregular “不规则的”。故填irregular。 2．which　考查定语从句的引导词。设空处引导非限制性定语从句，解释说明先行词The earliest piece of guqin，指物，在从句中作主语。故填which。 3．dates　考查动词的时态和主谓一致。设空处为主句谓语动词，此处陈述客观事实，用一般现在时，主语为The earliest piece of guqin，谓语动词用第三人称单数，date back to意为“追溯到”，无被动形式。故填dates。 课时作业(五) 45 4．appearance　考查词性转换。形容词性物主代词its修饰名词。故填appearance。 5．demanding　考查词性转换。设空处应用形容词作表语。demanding “要求高的”。故填demanding。 6．with　考查介词。句意：振动被抑制，产生一种起伏和持久的韵味，其间有丰富的空音符。表示“带有，具有”应用介词with。故填with。 7．was favored　考查动词的时态、语态和主谓一致。根据时间状语in ancient China可知，此处用一般过去时，主语为The guqin，和favor为被动关系，应用被动语态，主语为单数名词，be动词用was。故填was favored。 课时作业(五) 46 8．what　考查宾语从句的连接词。设空处引导宾语从句，从句缺少宾语，指代所表达的内容，应用连接代词what引导。故填what。 9．a　考查冠词。句意：这种深刻的理解在他们之间形成了一条牢固的纽带，他们成了亲密的朋友。bond为可数名词，此处表示泛指，应用不定冠词，且strong的发音以辅音音素开头。故填a。 10．compositions　考查词性转换。设空处应用名词作宾语，composition意为“作品”，为可数名词，one of后跟可数名词复数。故填compositions。 课时作业(五) 47 Ⅲ　概要写作 阅读下面短文，根据其内容写一篇60词左右的内容概要。 Getting rid of dirt, in the opinion of most people, is a good thing. However, there is nothing fixed about attitudes to dirt. In the early 16th century, people thought that dirt on the skin was a means to block out disease, as medical opinion had it that washing off dirt with hot water could open up the skin and let ills in. A particular danger was thought to lie in public baths. By 1538, the French king had closed the bath houses in his kingdom. So did the king of England in 1546. Thus began a long time when the rich and the poor in Europe lived with dirt in a friendly way. Henry Ⅳ， King of France, was famously dirty. Upon learning that a nobleman had taken a bath, the king ordered that, to avoid the attack of disease, the nobleman should not go out. 课时作业(五) 48 Though the belief in the advantage of dirt was long­lived, dirt has no longer been regarded as a nice neighbor ever since the 18th century. Scientifically speaking, cleaning away dirt is good to health. Clean water supply and hand washing are practical means of preventing disease. Yet, it seems that standards of cleanliness have moved beyond science since World War Ⅱ. Advertisements repeatedly sell the idea; clothes need to be whiter than white, cloths ever softer, surfaces to shine. Has the hate for dirt, however, gone too far? 课时作业(五) 49 Attitudes to dirt still differ hugely nowadays. Many first­time parents nervously try to warn their children off touching dirt, which might be responsible for the spread of disease. On the contrary, Mary Ruebush, an American immunologist (免疫学家), encourages children to play in the dirt to build up a strong immune system. And the latter position is gaining some reason. 课时作业(五) 50 ﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍﹍ 课时作业(五) 51 写前导读：本文是一篇说明文。文章主要讲述了在不同的历史时期人们对于泥的态度，以及泥对于身体健康的影响。 课时作业(五) 52 [精彩范文] People have mixed opinions towards dirt on our skin. (要点1) For a long time in history, people of some European countries, such as France, believed that dirt protected people from getting ill.(要点2) However, people began to change their attitudes to dirt about 200 years ago. People have been told that washing dirt off our body can keep us healthy. (要点3) But, some scientists believe that exposure to some dirt many help our immune system. (要点4) 课时作业(五) 53 【持续背记】 ①Upon the arrival of the spring, beautiful birds would sing happily in the park. 春天一到，美丽的鸟儿就会在公园里欢快地歌唱。 ②By getting actively involved in this activity, not only did we promote our friendship, but we also enriched our school life. 通过积极参加这次活动，我们不仅促进了我们的友谊，而且丰富了我们的学校生活。 课时作业(五) 54 ③Despite the new science, many of us still need to think twice about bringing our dogs, cats or indoor pigs into our beds. 尽管有新的科学理论(认为和宠物共眠有益)，但是我们大多数人在和狗、猫或宠物猪同睡之前还是要三思。 课时作业(五) 55 【持续积累】 课时作业(五) 56 R $$