Unit 2 Period Three Discovering Useful Structures(PPT课件)-【满分思维】2026-2027学年高中英语必修第一册配套课件（人教版）

Period Three Discovering Useful Structures 1 语法归纳 课后习题 2 【语境感悟】 阅读以下有关“旅行”的短文，感知加黑部分，并回答其后的问题。 I'm really excited about my trip to Hainan Island. I ①am setting off for Sanya, Hainan by plane next Thursday. Upon arrival, I ②will go to the famous Tianya Haijiao scenic spot. The day after, I ③am visiting the Wuzhizhou Island. Before I leave Hainan Island, I ④am to take a walk along the beautiful beaches in Sanya in the early morning. I'm sure this journey to Hainan will be an unforgettable experience. 3 【自主归纳】 以上语段中，①“am setting off”和③“am visiting”使用____________ 表将来;②“will go”使用“_______________”结构表将来;④“am to take”使用“__________”结构表将来。 现在进行时 will +动词原形 be to do 4 现在进行时表示将来 现在进行时表示将来主要用于表示按计划或安排将要发生的 动作或事件。这种用法给人一种期待感,常表示最近或较近的将来。 一、用于现在进行时表示将来的动词 1.表示位置转移的动词或动词词组,如arrive, come,get (to),leave, return, start, travel, take off, fly, see off等。 语 法 归 纳 5 We’re starting for Shanghai this afternoon. 今天下午我们将动身去上海。 Our flight is taking off and let’s hurry up or we will miss it. 我们的航班要起飞了,快点,否则我们就赶不上了。 语 法 归 纳 6 2.表示非位移的动词,如do, buy, meet, have, play, publish, spend等。 此时句中一般要有表示将来的时间状语。 The boy is meeting his friend this afternoon. 这个男孩今天下午要去见他的朋友。 They are spending their next summer holiday in Guilin. 他们要在桂林过下个暑假。 语 法 归 纳 7 【及时演练1】——翻译句子 (1)我们将在本周末去游览那个著名的旅游胜地。 ________________________________________________________ (2)我今天下午退房,然后去机场。 ________________________________________________________ We are visiting the famous tourist destination this weekend. I'm checking out this afternoon and leaving for the airport. 语 法 归 纳 8 二、表示将来意义的其他方式 1.will/shall do单纯地表示将来,说明对未来事情发生的“预见性”,可用 于说话时临时想到或决定的事。 —Where is the telephone book? —I'll go and get it for you. “电话号码簿在哪里?” “我去给你拿。” 语 法 归 纳 9 2.be going to do表示现在的打算、意图;也可表示预料在最近将会 发生的事。 We're going to watch the football game this afternoon. 我们打算今天下午看足球赛。 3. be to do表示预定、按计划或安排将会发生,也可表示将来必定发生 或表示命令等。 The meeting is to take place next Monday. 会议定于下周一举行。 语 法 归 纳 10 4. be about to do意为“刚要,正要”, 表示即将发生的动作,不与具体 时间连用,常与when搭配。构成:be about to do…when…,意为“正要 做……就在这时……”。 She was about to leave when some guests came. 她刚要离开,就在这时一些客人来了。 The concert is about to begin. 音乐会即将开始。 语 法 归 纳 11 【及时演练2】——翻译句子 (1)昨天我正要去购物,这时姐姐打来了电话。 __________________________________________________________ (2)我刚要打个电话给你,你就敲门了。 ____________________________________________________________ Yesterday, I was about to go shopping when my sister called me. I was about to phone/call you when you knocked on the door. 语 法 归 纳 12 一般现在时表示将来 1.客观性较强,多指按时刻表或规定要发生的动作或事件;谓语动词多 为表示“出发,到达”等的动词或动词词组,如arrive, leave, start, go out, take off等。 The flight to Shanghai takes off at 3:00 pm.(时刻表) 去上海的航班下午3点起飞。 语 法 归 纳 13 2.用于条件、时间及让步状语从句中。 It will be five years before the project is completed. (时间状语从句) 五年后这项工程才能完成。 I’ll go camping if it is fine tomorrow. (条件状语从句) 如果明天天气好,我就去野营。 【及时演练3】——单句填空 (1)The train _______ (leave) at six tomorrow morning. (2)I'll write you as soon as I _____ (get) there. leaves get 语 法 归 纳 14 【实战演练】 Ⅰ用所给词的适当形式填空 1.The foreign guests 　　　　　　　　(arrive) in Beijing tonight.  2.The man who gave a lecture last October 　　　　　　　(come) to our school tomorrow.  3.He 　　　　　　(leave) Beijing for London. His wife 　　　　　　 (expect) their next reunion in Beijing.  4.Our train 　　　　(leave) at 8:00 am, so we have an hour left.  5.Her train leaves at 11:30 am,and Bob 　　　　　　(see) her off.  are arriving is coming is leaving is expecting leaves is seeing 语 法 归 纳 15 6. —I’m sorry. I forgot to post the letter for you. —Never mind. I 　　　　　　(post) it myself this afternoon.  7.Do you know how they will use the product we 　　　　　　　 (make) at present?  8.Hurry up! Mark and Carol 　　　　　　　(expect) us.  9. —When are you leaving for Shanghai? —My plane 　　　　(take) off at 10:00 am.  10.Now she 　　　　　　　　(complain) about her living conditions and low salary.  will post are making are expecting takes is complaining 语 法 归 纳 16 Ⅱ语法与写作 1.Do you know which city on Hainan Island 　　　　　　　　　? (fly)  你知道他们要飞往海南岛的哪个城市吗? 2.Helen 　　　　　　 next month so 　　　　　　　　　 a new housemate. (leave; look for)  海伦下个月要离开了,因此我们正在找一个新的合住者。 3.A scientist 　　　　　　　　　　　 the students. I’d like to go and listen to it. (give)  一位科学家正在给同学们做报告,我想去听。 they are flying to is leaving we're looking for is giving a talk to 语 法 归 纳 17 4.Would you tell me   on the flight from Hong Kong today?(arrive) 你能告诉我李先生今天是否会乘坐来自香港的航班到达吗? 5.My car 　　　　　　　　　　　. I have to go and refill my car. (run)  我的车快没油了,我得去给它加油。 if Mr Li is arriving/will arrive is running out of gas 语 法 归 纳 18 课 后 习 题 19 Ⅰ单句填空(每小题1.5分，满分15分) 1.Jane, I hear you 　　　　　　　　(travel) to China. Have you got everything right?  2.Ladies and gentlemen, please fasten your seat belts. The plane 　　　　　　(take) off.　  3.Mr Black 　　　　　　(leave) for Shanghai in a few days. Do you know when the earliest plane takes off on Sunday?  are travelling is taking is leaving 1 2 3 4 5 6 7 8 9 10 课 后 习 题 20 4.Her nervousness quickly 　　　　　　　(disappear) once she was on stage.  5.I’m busy right now. I 　　　　　(fill) in an application form for a new job.  6.The water supply has been cut off because the workers 　　 　　　(repair) one of the main pipes.  7.Please don’t make so much noise. The baby 　　　　　　(sleep) now.  8.I 　　　　　　(stay) at a friend’s house for the time being.  disappeared am filling are repairing is sleeping am staying 1 2 3 4 5 6 7 8 9 10 课 后 习 题 21 9.She 　　　　　　 (eat) very little food every day because her doctor advises her to go on a diet.  10.Selecting a mobile phone for personal use is no easy task because technology 　　　　　　　(change) so rapidly.  is eating/eats is changing 1 2 3 4 5 6 7 8 9 10 课 后 习 题 22 Ⅱ句型训练(每小题3分，满分15分) 1.It’s late autumn. The weather 　　　　　　　　　　　　　　. (get)  深秋了,天气正变得越来越冷。 2.I don’t really work here; I 　　　　　　　　　　　 until the new secretary arrives. (help out)  我其实不是在这里工作,我只是在帮忙,直到新秘书来为止。 3.She 　　　　　　　　　　　　　　 these days. She has no time even to read newspapers. (prepare for)  这些天她正在准备考试,甚至连看报纸的时间都没有。 is getting colder and colder am just helping out is preparing for the exam 1 2 3 4 5 课 后 习 题 23 4.I lost my key yesterday. Now 　　　　　　　　　　　　. (look for)  昨天我把钥匙丢了,现在我正在找它。 5.Betty 　　　　　　　　 Guangzhou by plane at 3:00 this afternoon. Her brother Bob 　　　　　　　　　　. It’s half past one now. They 　　　　　　　 a taxi outside the school gate. (leave for; see off; wait for)  贝蒂今天下午3点要乘飞机去广州。她哥哥鲍勃要为她送行。现在 是一点半。他们正在校门外等出租车。 I'm looking for it is leaving for is seeing her off are waiting for 1 2 3 4 5 课 后 习 题 24 Ⅲ 阅读理解(每小题2.5分，满分10分) [2026·河北省大数据应用调研高一阶段性联合测评] With the rise of global travel, ecotourism has become a popular and meaningful choice. Unlike traditional tourism that may hurt the environment, ecotourism refers to responsible travel to natural areas. It aims to protect the ecosystem and support local communities, making it a win-win for travellers and the planet. Ecotourism brings great benefits. For the environment, it 1 2 3 4 课 后 习 题 25 reduces pollution and protects endangered species. For example, in Costa Rica’s rainforests, ecotourism projects have helped protect monkey habitats (栖息地). Travellers follow rules like not leaving rubbish or hurting wildlife, helping keep natural places as they are. For local people, it creates jobs in guide services and hotels. This makes their lives better and makes them want to protect their hometowns more. To practise ecotourism well, travellers need to take simple steps. Start by choosing tour companies that focus on environmental 1 2 3 4 课 后 习 题 protection, as these providers usually design trips with minimal ecological influence. It’s also important to respect local cultures and customs—for example, dressing properly when visiting special places shows respect for the community’s traditions. Additionally, using eco-friendly products like reusable water bottles and avoiding single-use plastics can cut down waste during the journey. However, ecotourism still faces certain challenges. A main problem is that it’s hard to balance protecting the environment and economic benefits: to get short-term benefits, some local 1 2 3 4 课 后 习 题 communities may lower environmental standards, which in turn leads to over-development of supporting facilities (设施)—such development finally upsets the natural balance. Also, building basic structures like roads and accommodations in sensitive (敏感的) ecological areas harms local plants and animals directly as it destroys their homes. In short, ecotourism is more than just a trip. It’s a way to connect with nature and help protect it. As students, we can start with small but useful actions: sharing ecotourism knowledge, choosing nearby 1 2 3 4 课 后 习 题 eco-friendly places for school trips, or even bringing reusable bags when visiting local parks. These small steps will make our travels more meaningful and environmentally friendly. 【文章大意】本文是一篇说明文。文章介绍了生态旅游的概念,它 与可能破坏环境的传统旅游不同,旨在保护生态系统和支持当地社区。 同时作者呼吁学生从小事做起,践行生态旅游,使旅行更有意义且环保。 1 2 3 4 课 后 习 题 ( )1. What makes ecotourism different from traditional tourism? A.It focuses on global travel. B.It offers trips to rainforests. C.It costs travellers less money. D.It connects travel and protection. √ 1 2 3 4 课 后 习 题 30 [解析] 细节理解题。根据文章第一段中的“Unlike traditional tourism that may hurt the environment, ecotourism refers to responsible travel to natural areas. It aims to protect the ecosystem and support local communities, making it a win-win for travellers and the planet.”可知, 生态旅游与传统旅游的不同之处在于它将旅行和保护联系在一起, 既能让旅行者享受旅行,又能保护生态环境和支持当地社区。故选D。 1 2 3 4 课 后 习 题 31 ( )2. What does the underlined word “minimal” in Paragraph 3 probably mean? A.Very small.　 　 B.Quite certain. C.Rather difficult. D.Extremely quick. √ 1 2 3 4 课 后 习 题 32 [解析] 词义猜测题。根据文章第三段中的“Start by choosing tour companies that focus on environmental protection, as these providers usually design trips with minimal ecological influence.”可知,专注于 环境保护的旅游公司设计的旅行对生态的影响应该是很小的,因此 minimal在这里的意思是“非常小的”。选项A“Very small.”(非常小。) 与画线词意思相近。故选A。 1 2 3 4 课 后 习 题 33 ( )3. Why may some local communities lower environmental standards? A.To protect wildlife. B.To get quick benefits. C.To follow local customs. D.To save eco-friendly products. √ 1 2 3 4 课 后 习 题 34 [解析] 细节理解题。根据文章第四段中的“A main problem is that it’s hard to balance protecting the environment and economic benefits: to get short-term benefits, some local communities may lower environmental standards…”可知,当地一些社区可能会降低环境标准 来获得短期利益,即快速获得经济收益。故选B。 1 2 3 4 课 后 习 题 35 ( )4. What is the best title for the text? A.Travel ways: a hard choice for tourists B.Ecotourism: a responsible way of travelling　 C.Traditional tourism: a harmful travel choice　 D.Travel companies: a misleading marketing tool √ 1 2 3 4 课 后 习 题 36 [解析] 主旨大意题。根据文章第一段中的“With the rise of global travel, ecotourism has become a popular and meaningful choice.” 以及全文内容可知,文章主要介绍了生态旅游的定义、好处、实践 方法以及面临的挑战,强调了生态旅游是一种负责任的旅行方式,既 能让旅行者享受旅行,又能保护生态环境和支持当地社区。选项B “Ecotourism: a responsible way of travelling”(生态旅游:一种负责任 的旅行方式)最能概括文章的主旨大意,适合用作标题。故选B。 1 2 3 4 课 后 习 题 37 Ⅳ 阅读七选五(每小题2.5分，满分12.5分) [2026·广东和美联盟高一月考] The value of travel Travel is not only about reaching a destination but also about experiencing the world in new ways. Through each journey, you discover cultures, stories, and values that can broaden your mind. 1.　　　　. A 2025 study reported that open-minded travel promotes growth and cross-cultural connections among students. To help you unlock these benefits, here are some tips to make your journey meaningful.  D 1 2 3 4 5 课 后 习 题 38 Plan ahead but stay adaptable Having a plan gives you direction, but travel is full of surprises. Unexpected changes may challenge your ideas while also creating new opportunities. If you hold too tightly to your original plan, you may miss out on these chances. 2.　　　　. By doing so, you enjoy both safety and discovery. 3.　　　  Every community has traditions and lifestyles worth noticing, from food and music to simple greetings. Showing honour through small E A 1 2 3 4 5 课 后 习 题 actions, like saying hello in the local language, can leave a positive impression. These gestures help you build genuine connections with students you meet. Slow down and notice the details Rather than rushing through famous spots, try slowing down to notice what might otherwise be ignored. The sound of street music, the smell of local dishes, or even a short chat with a shop owner may remain in your memory far longer than any postcard photo. 4.　　　.  F 1 2 3 4 5 课 后 习 题 Reflect on your journey Writing a diary or taking photos allows you to reflect on what you have learned on the way. 5.　　　　. Such reflection strengthens your understanding and can inspire others to begin their own journeys.  A.Respect local traditions B.Focus on daily lifestyles C.Try to enjoy the famous sights in detail D.It can teach you lessons no classroom offers 1 2 3 4 5 G 课 后 习 题 E.Revising your plan when needed helps you adapt　 F.These small experiences often leave the deepest impressions G.This practice also provides a way to share your experiences with others 1 2 3 4 5 【文章大意】本文是一篇说明文。文章阐述旅行不仅是抵达目的地, 更能拓宽视野、促进成长与跨文化联结,还给出提前规划但保持灵活、 尊重当地传统等实用建议,助力打造有意义的旅程。 课 后 习 题 1.___ D [解析] 根据上文“Travel is not only about reaching a destination but also about experiencing the world in new ways. Through each journey, you discover cultures, stories, and values that can broaden your mind.” 以及后文“A 2025 study reported that open-minded travel promotes growth and cross-cultural connections among students. To help you unlock these benefits, here are some tips to make your journey meaningful.”可知,空格前提到旅行能发现文化、故事和价值观,拓宽 1 2 3 4 5 课 后 习 题 43 视野;空格后提到研究表明开放的旅行能促进学生成长和跨文化联系。 选项D“它能教给你课堂上无法获得的知识”衔接“拓宽视野”与“促进 成长”,体现旅行的独特价值,逻辑连贯。故选D。 1 2 3 4 5 课 后 习 题 44 2.___ E [解析] 根据上文“Having a plan gives you direction, but travel is full of surprises. Unexpected changes may challenge your ideas while also creating new opportunities. If you hold too tightly to your original plan, you may miss out on these chances.”以及后文“By doing so, you enjoy both safety and discovery.”可知,空格前提到过度执着于原计划 会错失机会;空格后提到“既享受安全感,又能探索未知”。选项E“必要 时修改计划有助于适应变化”直接回应“不执着于原计划”,且引出后文 “平衡安全与探索”,符合“提前规划但保持灵活”的主题。故选E。 1 2 3 4 5 课 后 习 题 45 3.___ A [解析] 根据后文“Every community has traditions and lifestyles worth noticing, from food and music to simple greetings. Showing honour through small actions, like saying hello in the local language, can leave a positive impression. These gestures help you build genuine connections with students you meet.”可知,空格处为段落主旨句,后文 提到每个社区都有值得关注的传统和生活方式,通过小行动表达尊重, 建立真诚联系。选项A“尊重当地传统”精准概括段落核心。故选A。 1 2 3 4 5 课 后 习 题 46 4.___ F [解析] 根据上文“Rather than rushing through famous spots, try slowing down to notice what might otherwise be ignored. The sound of street music, the smell of local dishes, or even a short chat with a shop owner may remain in your memory far longer than any postcard photo.”可知,空格前提到放慢节奏并关注细节,并提到街头音乐、当地 美食气味、与店主的简短聊天等易被忽视的内容。选项F“这些微小的 经历往往留下最深刻的印象”承接前文“易被忽视的细节”,呼应“比明信片 照片更难忘”,逻辑通顺。故选F。 1 2 3 4 5 课 后 习 题 47 5.___ G [解析] 根据上文“Writing a diary or taking photos allows you to reflect on what you have learned on the way.”以及后文“Such reflection strengthens your understanding and can inspire others to begin their own journeys.”可知,空格前提及写日记或拍照能反思旅途所学;空格 后提到“反思能加深理解,激励他人”。选项G“这种做法也提供了与 他人分享经历的方式”,衔接“反思”与“激励他人”,补充了记录旅行的 另一意义,且also体现递进关系。故选G。 1 2 3 4 5 课 后 习 题 48 Ⅴ 完形填空(每小题1分，满分15分) [2026·浙江温州新力量联盟高一期中联考] Last summer, my family and I finally made our long-held dream come true—a trip to Peru. For weeks, we had been 　1　 our trip online, reading travel blogs and guidebooks. We were all extremely 　2　 about exploring this beautiful country.  Our first step was to 　3　 our flights and accommodation. We decided to 　4　 an early flight to Lima, the capital, to maximize our time. Upon arrival, we were immediately drawn to the view of the 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 课 后 习 题 49 city even before 　5　 at our hotel—the mix of modern buildings and ancient architecture was unforgettable.  The main 　6　 of our trip was, of course, Machu Picchu. To get there, we had to take a train from Cusco. The train ride itself was a truly 　7　 experience. The landscape of the Andes Mountains was absolutely impressive. We spent the journey 　8　 the various sights along the way out of the window, amazed.  When we 　9　 at the ancient Inca city, we were speechless. Standing among the 　10　 stone ruins (废墟), we could almost feel 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 课 后 习 题 the history around us. Our guide told us many 　11　 stories about the Incas, which made the experience even more meaningful.  Besides the famous sites, we also enjoyed the local 　12　. We tried ceviche, a traditional dish made from fresh raw (未加工的) fish, and found it delicious. The local people were very 　13　 and welcoming. We even learned a few basic Spanish words to 　14　 with them, which they really appreciated.  This trip was not just a holiday; it was a life-changing 　15　. It broadened our horizons and gave us memories that we will cherish 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 课 后 习 题 forever. We are already starting to think about our next adventure!  【文章大意】本文是一篇记叙文。文章主要讲述了作者一家去秘鲁 旅行的经历。 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 课 后 习 题 ( )1. A.packing　　B.planning C.requesting D.renting [解析] 根据前文“…my family and I finally made our long-held dream come true—a trip to Peru.”可知,作者一家在网上规划旅行。故选B。 pack打包;plan规划;request要求;rent租用。 ( )2. A.excited B.annoyed C.confused D.frightened [解析] 根据后文about exploring this beautiful country可知,他们对探索 这个美丽的国家感到兴奋。故选A。 excited兴奋的;annoyed恼怒的; confused困惑的;frightened害怕的。 √ √ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 课 后 习 题 53 ( )3. A.cancel B.recognize C.book D.find [解析] 根据后文our flights and accommodation可知,去旅游前需要预 订航班和住宿。故选C。 cancel取消;recognize识别;book预订;find找到。 ( )4. A.take B.miss C.wait D.contact [解析] 根据后文an early flight to Lima可知,此处指乘坐早班飞机。 take a flight是固定搭配,意为“搭乘航班”。故选A。take乘坐;miss错过; wait等待;contact联系。 √ √ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 课 后 习 题 54 ( )5. A.making up B.checking in C.checking out D.working out [解析] 根据后文at our hotel可知,到酒店后需要办理入住手续。故选B。 make up组成;check in办理入住;check out退房;work out算出。 ( )6. A.detail B.flight C.path D.destination [解析] 根据后文“…of our trip was, of course, Machu Picchu.”可知, 马丘比丘是此行的主要目的地。故选D。 detail细节;flight航班;path 道路;destination目的地。 √ √ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 课 后 习 题 55 ( )7. A.unique B.formal C.economic D.awkward [解析] 根据后文“The landscape of the Andes Mountains was absolutely impressive.”可知,安第斯山脉的风景令人印象深刻,说明乘火车的体验 独特。故选A。 unique独特的;formal正式的;economic经济的;awkward 尴尬的。 √ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 课 后 习 题 56 ( )8. A.walking B.admiring C.applying D.moving [解析] 根据后文“…the various sights along the way out of the window…”可知,他们在坐火车时欣赏窗外的景色。故选B。walk散步; admire欣赏;apply申请;move移动。 ( )9. A.left B.arrived C.stayed D.returned [解析] 根据后文“Standing among the…stone ruins (废墟), we could almost feel the history around us.”可知,他们到达古老的印加城市,感受 到了独特的历史。故选B。 leave离开;arrive到达;stay停留;return返回。 √ √ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 课 后 习 题 57 ( )10. A.modern B.official C.ancient D.expensive [解析] 根据上文the ancient Inca city可知,此处指古老的石头废墟。 故选C。modern现代的;official官方的;ancient古老的;expensive昂贵的。 √ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 课 后 习 题 58 ( )11. A.confusing B.boring C.amazing D.frightening [解析] 根据后文“…which made the experience even more meaningful.” 可知,导游讲的故事让这次经历更有意义,说明故事很神奇。故选C。 confusing令人困惑的;boring无聊的;amazing令人惊奇的;frightening 可怕的。 √ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 课 后 习 题 59 ( )12. A.language B.weather C.culture D.civilization [解析] 根据后文“We tried ceviche, a traditional dish made from fresh raw (未加工的) fish…”可知,他们尝试当地食物,说明喜欢当地文化。 故选C。 language语言;weather天气;culture文化;civilization文明。 ( )13. A.rude B.friendly C.shy D.positive [解析] 根据后文and welcoming可知,当地人友好热情。故选B。 rude 粗鲁的;friendly友好的;shy害羞的;positive积极的。 √ √ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 课 后 习 题 60 ( )14. A.argue B.hike C.communicate D.comment [解析] 根据上文“We even learned a few basic Spanish words…”可知, 作者一家学习基础的西班牙语单词是为了和当地人交流。故选C。 argue争论;hike远足;communicate交流;comment评论。 ( )15. A.experience B.credit C.source D.economy [解析] 根据上文“This trip was not just a holiday; it was a life- changing…”可知,这次旅行是一次改变人生的经历。故选A。 experience经历;credit信用;source来源;economy经济。 √ √ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 课 后 习 题 61 $