内容正文:
作业(十五)
Section II
Developing ideas & Presenting ideas
层级基础知识自测
2.如果有必要,我们学校将为学生提供语言培训课
程。(省略句)
I.单词拼写
, our school will provide the
1. The machines contain high levels of lead(铅)
students with the language training courses.
and other dangerous
(物质),which are
3.沿途全是参天大树,其中一些有大约一百年的历
harmful to our health.
史。(倒装句)
2. The apartment is far too small for us.
, some of them
(另外), it is too far from our company.
with a history of around 1oo years.
3. The athletes are required to stand with their feet
IV. 课文语法填空
apart and their hands facing
(向上).
It is estimated 1.
three million
4. After two months of
(钻探,勘探),oil
shipwrecks are lying under waters across the
was found off the coast.
globe. All of them represent attempts 2.
5. The city's average rainfall was 17
(explore ) Earth's furthest corners over the
(毫米)in the 24 hours up to Friday morning.
centuries. With the exploration of the oceans, we
II. 单句语法填空
are continuing to make new discoveries in various
1. There's absolutely no regulation of cigarettes to
scientific fields. Many archaeological finds 3.
make sure that they don't include poisonous
(make) in shallow waters near the coast.
(substance).
However, we are only beginning to overcome the
challenges of pressure, 4.
2. They had accidentally damaged a gas pipe while
(dark) and
(drill). Luckily, no one was seriously
extreme cold at vast depths.
injured.
(amaze) biological discoveries are
3. These ancient messages and sketches offer a
also being made. The dark zones of the oceans may
window
the daily routine and interests
contain up to 90 per cent of the planet's fish. In the
of the people in ancient times.
very deepest ocean trenches, there is still life to be
4. There are many challenges at the very depths of
found. These discoveries help us understand the
the ocean and there are also many parts that are
capacity for life on our planet, even in 6.
the reach of human exploration
most extreme circumstances.
Besides, the oceans are a valuable source of
5. Breathing such polluted air is eauivalent
natural resources, some of which are 7.
smoking ten cigarettes a day.
(stand) a
(complete) new to us. China has discovered an ice-
6. At the top of the hill
like substance, known 8. _
“fire ice”,
weather station.
under the South China Sea. China's underwater
7. If more people join in the trend to ride bicycles
vessels have been exploring waters at depths of
to work,then the air quality will be improved
thousands of metres. The research 9.
(notable).
(conduct) by these vessels not only gives scientists
8. Tom is a great basketball player. He holds the
a greater understanding of how the sea bed was
school record
most points in a season
formed, but also helps identify areas for deep-sea
in our school.
drilling,10.
(take) deep-sea exploration
9. If you continue
(complain)
into a whole new era.
about your study, you will never make progress
in it.
层级②素养能力提升
10. The ship loaded with cargoes will set sail
I. 阅读理解
New Orleans tomorrow morning.
A
III.完成句子
“Experts using a high-tech laser scanner(激光
1.人们希望这些发现能为了解宇宙的起源提供新
扫描仪) have discovered thousands of abandoned
的窗口。(形式主语)
ancient Maya buildings under the thick forests of
northern Guatemala," officials said on Thursday.
the origin of the universe.
Some 6o, ooo buildings were found over the past
43
·英语·选择性必修 第四册(配WY版)
two years in a scan of an area in the northern
C. Their pyramid was made of a hill.
department of El Peten between Mexico and
D. They might be a nation with a surprisingly
Belize, said Marcello Canuto, an archaeologist at
large population.
Tulane University in the United States and one of
4. What is the author's main purpose in writing the
the project's lead researchers.
text?
These findings were a"breakthrough in Maya
A. To inform readers of the new discoveries
archaeology”,Canuto said.
about the Maya.
The new discoveries in this Central American
B. To introduce a new method used to discover
country included city centers with sidewalks,
Maya buildings.
homes, wide steps, farming facilities and so on,
C. To show Maya development was of great
said Canuto.
influence.
Among the finds was a 30-meter high pyramid
D. To tell us a new documentary will be
that had been earlier recognized as a natural hill in
launched on TV in Feb.
Tikal. Also discovered in Tikal were a series of
B
holes and a 14-kilometer-long wall.
One of the oldest archaeological sites in the
Maya civilisation reached its height in what is
Americas has been discovered in Cooper's Ferry in
present-day southern Mexico, Guatemala, and
western Idaho, according to a study published in
parts of Belize, El Salvador and Honduras between
the journal Science.Radiocarbon(放射性碳)
250 CE and 95o CE.“Researchers now believe that
dating shows that people were creating tools and
the Maya had a population of 10 million, which is
hunting animals in Cooper's Ferry between 15,000
much higher than previous judgment," Canuto
and 16,o0o years ago.
said.
Until a couple of decades ago, Clovis stone
The project depended on a remote sensing
tools, which are generally about 13,oo0 years old.
method known as LIDAR (Light Detection and
were considered to be the first human technology
Ranging). Aircraft with a LIDAR scanner produced
in the Americas. Though dozens of sites claim to be
3D maps of the surface by using light in the form
what archaeologists call "pre-Clovis",Donald
of a laser beam.
Grayson, an archaeologist and professor at the
The technology
helped researchers discover
University of Washington, believes that to date
sites much
faster than using traditional
only a few are actually dated
archaeological methods. "Now it is no longer
Archaeologist Loren Davis, lead author of the
necessary to cut through the jungle to see what's
Science report, first dug at Cooper's Ferry in 1997
under it,"said Canuto.
as part of his PhD studies. He found a number of
Details of the research will appear in a
stone points that could have been fixed to the
documentary to air on February 11 on the National
handle of a tool. Radiocarbon dating of bones and
Geographic TV channel, said Minister of Culture
charcoal (木炭) that were buried in the same small
and Sports Jose Luis Chea.
hole suggested these tools were up to 13,3o0 years
1. What did Canuto think of the new discoveries in
old. Davis returned about ten years later to lead a
the past two years?
further exploration of Cooper's Ferry because he
A. Crucial.
B. Frightening
still had some questions. He wanted to know if the
C. Annoying
D. Puzzling.
tools he found in the 199os were older than tools in
2. Which of the following is an advantage of
the Clovis tradition.
L.IDAR?
Over the last decade of excavation, Davis and
A. It saves money in discovering sites.
his team found evidence of heat-cracked rocks from
B. It is more convenient for researchers to cut
ancient campfires, workspaces for making and
through the jungle.
repairing tools, and parts of animal bones. In 2018
C. Explorers have to go deep into the jungle to
Davis' team sent some charcoal from an ancient
research.
campfire for radiocarbon dating and was surprised
D. Research can be done at a distance.
that it was in the 14, ooo-year-old age range. To
3. What can we know about the Maya according to
make sure those results were right, more materials
the new discoveries?
from Cooper's Ferry were tested.
A. They might live in Africa.
“Our results just kept on coming in older and
B. Their living area might be less developed
older and older,"Davis says. The deepest layer of
44
artifact-filled sediment(沉积物) at the site had an
his mother later
7 it to the authorities when
age range of about 15,o00 to 16,oo0 years old."I
she saw strange blue thin lines of fire rising from
just never thought that the site was going to be
the trees.
this old.”
Several locals including members of the fire
5. What can be learned about Clovis stone tools?
department went out to look into the scene and
A. They led to the new finding in Idaho.
8 an odd acorn-shaped object, the size of a
B. They were discovered several years ago.
small car with 9 writing on its surface.
C. They are no longer considered an important
Within a short space of time there were
discovery.
reports of a serious military 1o at the crash site
D. They are not the first human technology in
with army officials 11 ordinary people away
America.
from the scene while the object was being loaded
6. What did Loren Davis most probably realize
into a truck.
12 what crashed in Kecksburg that day
during his excavation in 1997?
more than 50 years ago continues to remain the
A. General exploration is needed in America.
subject of much controversy(争议) and 13.
B. Cooper's Ferry wasn't really worth digging.
Some people believe that it might have been a
C. The world's oldest tool was found in
crashed Soviet satellite or the remains of some
America.
experimental test flight that went horribly wrong.
D. People once lived in Cooper's Ferry 13, 300
There are even those who believe that the 14
years ago.
was evidence of alien visits.
7. What do Davis' words in the last paragraph
Whatever the 15 , the Kecksburg mystery
show?
is likely to last for many more years to come.
A. He doubted the results.
1. A. abandoned
B. lost
C. earned
B. He was a really good researcher.
D. changed
C. He was very surprised at the results.
2. A. caught
B. observed
C. picked
D. He would find evidence for his theory.
D. avoided
3. A. burned
8. What would be the best title for the text?
B. flew
C. rushed
A. The first human technology uncovered
D. moved
4. A. sightings
B. A new archaeological site discovered in America
B. damage
C. rumors
C. Human activity discovered in a 13, ooo-year-
D. panic
5. A. delighted
B. crowded
oldsite
C. connected
D. concerned
D. Idaho's archaeological site now among America's
6. A.areas
oldest
B.fields
C.caves
D. woods
II.完形填空
7. A. handed
B. reported
It has been several decades since the UFO
C. showed
D. recalled
raced across the US and crashed near Kecksburg
8. A. came across
B. laid out
Taken for nothing more than a meteor (流星)
C. looked for
D. set off
impact at the beginning, the famous event later
9. A. familiar
B. common
1 the nickname of "Pennsylvania's Roswell"
C. strange
D. meaningful
after the military was said to attempt to cover
10. A. training
B. investigation
it up.
C. absence
D. presence
The incident began on December 9, 1965
11. A. begging
B. forbidding
C. ordering
when thousands of people across several states
D. allowing
2 a strange fireball which dropped "hot metal
12. A.Exactly
B. Naturally
C. Possibly
pieces" as it 3 through the sky.
D. Especially
13. A. attack
Despite the 4 being fairly widespread, it
B. debate
C. criticism
was the small town of Kecksburg in Pennsylvania
D. suspicion
14. A. object
that would become most closely 5 with the
B. creature
C. theory
incident.
D. scene
15.A. case
It started when a young local boy claimed that
B. purpose
C. design
he had seen an object landing in nearby 6 and
D. appearance
451.B 细节理解题。根据第二段中的“They sailedon the
: 5.B 下文是对设空处的补充说明。根据上文“TheUS
Plastiki...the bottles in place.”可知,Plastiki号是由绿色
Coast Guard prefers to dispel any idea of supernatural
材料(环保材料)制成的。故选B。
forces at play.”以及下文“They think that human error.
2.D 推理判断题。根据第四段中的“However,hismost
natural forces, and coincidence are reasons responsible for
important objective... pollution had become.”可知,他们
these unsolveddisasters.”可知,美国海岸警卫队主张消除
航行的目的是强调塑料垃圾问题。故选D。
那些超自然力量的观点,更倾向于接受合乎逻辑的观点。
3.D 推理判断题。根据第五段内容以及最后一段中的“The
故选B。
Plastiki's journey had shown... valuable resources."可以推知,
III.,[语篇解读]本文是一篇说明文。文章介绍了世界上的
Plastiki号的航行具有挑战性但意义重大。故选D。
大部分海洋仍然是个迷,新技术正在帮助科学家探索这些隐
4.C 推理判断题。根据最后一段中的“ThePlastiki's
藏的世界。
journey had shown that... valuable resources.”可推知,塑
1. hasbeenexplored 考查动词的时态、语态和主谓一致
料垃圾可以变成财富。故选C.
B-[语篇解读] 本文是一篇说明文。文章主要介绍了利
根据sofar可知,句子时态用现在完成时,又因主谓之间
是被动关系,应用被动语态,且主语5percentof it是单
用声音测量海洋湿度的相关内容。由于声音在不同温度的
数,所以用现在完成时的被动语态hasbeenexplored。
海水中传播速度不一样,所以能用它检测海洋变暖。
5.B 细节理解题。根据第二段中的“Satellite observations
2.than考查介词。根据more修饰比较级可知,空处应用
表示比较的介词than。
cannot enter very deep below the surface.”可知,人们会利
3. hidden 考查形容词。根据worlds可知,空处应用形容词
用卫星去收集海洋湿度方面的数据,故B项正确。根据第
二段中的"Ship-based observations capture only snapshots
作定语。
4. of 考查介词。ahuge varietyof是固定短语,意为“各种
in time over a tiny portion of the water.”可知,船只能检测
各样的”。
到一小部分水域,故A项错误;根据第二段中的“Themost
5.that/which考查定语从句。分析句子结构可知,空处引
detailed picture of ocean heat comes from Argo... they
导定语从句,从句中缺少主语,先行词chemicals指物,应
cannot sample deeper parts of the ocean.”可知,Argo 不能
用关系词that或which。
进入最深的海域,故C项错误;D项文中未提及。
6.deepest 考查形容词的最高级。the后跟形容词的最高级
6.A 细节理解题。根据第三段中的“Because soundtravels
修饰名词location。
faster in warmer water, differences in speed can reveal
7. reached 考查动词的时态。根据In2012可知,句子描述
changingtemperatures.”可知,由于声音在不同温度的水
域传播速度不同,所以速度之间的差异可以显示温度的变
过去的动作,应用一般过去时reached。
化,因此,声音可以被用来检测海洋变暖,故A项正确。
8. to complete 考查非谓语动词。the first后用动词不定式
7.D细节理解题。根据第四段中的“Caltechresearcher
作后置定语。
Wenbo Wu thought to monitor low-frequency sound waves
9. photos 考查名词复数。photo是可数名词,前面无冠词,
因此应用名词复数photos。
sent out by earthquakes below the seafloor."和最后一段中
的"Meanwhile Simons and his colleagues ... more
10.opening 考查非谓语动词。of为介词,其后应用动名词
作宾语。
earthquake sounds.”可知,Wu和Simons都使用了新的研
作业(十五)
Section I
究方法,故D项正确。
Developing ideas &
8.C 标题归纳题。根据本文的中心句“Soundmayoffera
Presenting ideas
creative way to take the ocean's temperature.”和其他内容
[层级1 基础知识自测]
可知,本文主要介绍了利用声音测量海洋温度的研究方
I. 1. substances 2. Furthermore 3. upwards 4. drilling
法,故C项最适合作本文的标题。
II.[语篇解读]本文是一篇说明文。文章介绍了人们对美
5. millimetre
II. 1. substances 2. drilling 3. into 4. beyond 5. to
国Flight19飞行中队在百慕大三角消失的原因持有的不同
观点。
6. stands 7. notably 8. for 9. to complain/complaining
10. for
1.G 设空处下文提到其中之一是美国Flight19飞行中队
III. 1. It is hoped that these discoveries can offer a new
的神秘消失,由此推知设空处说的是“Amongthem”中的
window into 2. If necessary 3. Along the road are thick
them的情况。分析选项可知G项与下文衔接紧密,下文
是G项中所说的“许多船和飞机神秘消失”的其中一个例
and tall trees
IV. 1. that 2. to explore 3. are made 4. darkness
子,且G项中的“unexplaineddisappearances”与下文中的
“mysterious disappearance”对应,下文中的“them”指代G
5. Amazing 6. the 7. completely 8. as 9. conducted
10. taking
项 中的"unexplained disappearances of many ships and
airplanes”.故选G。
[层级2 素养能力提升]
2. C 根据下文中的“One is the popular belief that
I.A--[语篇解读] 本文是一篇说明文。文章主要介绍
supernatural forces were at play."“Some theorize that...
了一项发现玛雅建筑的新技术。
Some theorizethat...”可知,本段讲的是人们对神秘消失
1. A 推理判断题。根据第一段中的“Some60,000
事件的看法。分析选项可知,C项中的“these
buildings were found over the past two years"和第二段中
disappearances”承接上一段最后提到的神秘消失现象,C
的"These findings were a 'breakthrough in Maya
项中的"two schools of thought on these disappearances"
archaeology'”可知,Canuto认为这些新发现是一个重大的
又引出下文关于神秘消失现象的观点,是对下文的概括,
突破。A项最符合Canuto的观点,故选A。
承上启下,符合语境,故选C。
2.D 细节理解题。根据倒数第二段内容可知,利用这项技术研
3.F 上一段介绍了人们关于神秘消失事件的其中一种观
究人员可以远程探索玛雅建筑,不用去丛林中了。故选D。
点。根据下文中的“This part of the Atlantic is subject to
3.D 细节理解题。根据第五段中的“Researchersnow
sudden storms...unpredictable conditions.”可知,下文提
believe that the Maya had a population of 10 million
到的内容都是从自然科学的角度给出的解释。分析选项
which is much higher than previous judgment"可知,玛雅
可知F项将前后两种观点进行了比较,说明从自然科学角
可能人口众多。故选D。
度给出的解释比上文中提到的超自然力量更合乎逻辑,承
4.B 推理判断题。根据文章的篇章结构可知,文章第一、二
接上文,同时引出下文对自然科学角度的解释的介绍,承
段引出了一项技术并说明了它的重要作用,第三、四、五段
上启下,符合语境。故选F。
通过列举利用这项技术发现的情况来突出这项技术的作
4. E 根据下文中的“People travel in this area... when
用,第六、七段介绍了这项技术的工作原理和优点,由此
conditionschange.”可知,下文对人为因素进行了介绍。E
可知文章的主要目的是介绍这项新技术。故选B。
项承接上文的环境因素,同时引出下文对人为因素的介
B[语篇解读] 本文是一篇说明文。考古学家在美国爱
绍,承上启下,说明除了上文提到的自然因素之外,还有人
达荷州西部发现的一个远古遗址被证明是美洲已知最古老
为因素在内。故选E.
的人类定居点之一。
5.D 细节理解题。根据第一段中的“Oneoftheoldest
Unit 6
Space and beyond
archaeological sites in the Americas has been discovered in
作业(十六)SectionI
Cooper'sFerry in western Idaho”和“Radiocarbon(放射性
Starting out &
碳)dating shows that people were creating tools and
Understanding ideas
hunting animals in Cooper's Ferry between 15, ooo and
[层级1 基础知识自测
16,000 years ago.”、第二段中的“Clovis stone tools,which
I. 1. shadows 2. unexceptional 3. suspended 4. crew
are generally about 13,oo0 years old”以及最后一段中的
5. screamed
“The deepest laver of artifact-filled sediment (沉积物) at
II.1. off 2. accustomed 3. on/over 4. suspension 5. in
the site had an age range of about 15,ooo to 16 o00 years
6. to 7. screaming 8. Tragically 9. on 10. unexceptional
old.”可知,克洛维斯遗址的时间大约是13000年前,而研
III. 1. However difficult/No matter how difficult it is to
完人员发现还有比克洛维斯遗址更早的遗迹,时间是
explore space 2. There's never any/no doubt that 3. is said
16000年前到15000年前之间。由此可知克洛维斯遗址
to have been translated
并不是美洲最古老的人类遗址。故选D。
IV. 1. has become 2. involved 3. because/as 4. to rekindle
6.D 细节理解题。根据第三段中的“Archaeologist Loren
5. a 6. tragically 7. most disastrous 8. were suspended
Davis... first dug at Cooper's Ferry in 1997 as part of his
9. in 10. exploration
[层级2 素养能力提升]
PhD studies. He found a number of stone points that could
I.A--[语篇解读] 本文主要介绍了科学家努力寻找火
have been fixed to the handle of a tool. Radiocarbon dating
星上存在生命的证据。
of bones and charcoal(木炭) that were buried in the same
1.C 细节理解题。根据第一段中的“NASA,Americas
small hole suggested these tools were up to 13,3oo years
space agency... that would be present if there once was or
old.”可知,在1997年的挖掘过程中,LorenDavis发现库
still is life on the planet”可知,NASA发现很久以前火星
珀渡船遗址中的人类活动可以追潮到距今13300年前。
上有地表水,而水又是生命所必需的,这使得科学家认为
故选D。
火星上曾经或仍然存在生命并试图找出证据。
7.C 推理判断题。根据最后一段中Davis的话“Ijust never
2.B 细节理解题。根据第二段中的“Boronisimportant
thought that the site was going to be this old.”可知,Loren
because it could help build... the basic parts of life"可知
确可以帮助构建生命基本组成部分之一的RNA分子,因
Davis没想到他研究的遗址那么古老,他的研究结果让他
此在火星上发现砌很重要,这可能证明有生命的存在。
自己感到很震惊。故选C。
3.D 细节理解题。根据第三段中的“Themicroscope
8.D 主旨大意题。根据第一段中的“One of the oldest
showed holes in the rocks caused by tiny living things
archaeological sites in the Americas has been discovered in
called microbes”和最后一段中的“The scientists hope to
Cooper's Ferry”“Radiocarbon(放射性碳)dating shows
get the same findings in the rocks from Mars as the ones
that people were creating tools and hunting animals in
they saw inthe ocean rocks”可知,火山岩石显示出了一些
Cooper's Ferry between 15,0o0 and 16,oo0 years ago."和
由微生物造成的洞,科学家希望研究火星岩石也可以得到
文章对该研究过程的介绍可知,本文主要介绍了库珀渡船
相同的发现,即科学家期待发现由微生物造成的润。
遗址是美洲最古老的人类定居点之一。D项最符合文意,
4.A 标题判断题。根据全文内容并结合文章前两句可知,
故选D。
本文主要介绍了科学家努力寻找火星上存在生命的证据,
II.[语篇解读] 本文是一篇说明文。文章介绍了1965年
故A项最适合作文章标题。
B-[语篇解读]本文是一篇说明文。介绍了一款头盏,
在美国发现不明飞行物的情况以及人们对它的猜测。
它将会给我们提供一个安静的个人空间。
1.C 结合上下文可知,此处是指这一事件获得(earn)了一
5.B 推理判断题。根据第一段中的“Now,youneedn't
个绰号。
worry, for the Helmfon will help you ignore noisy co
2. B 根据上文中的“thousands of people across several
workers andother distractions”可知,作者在文章的开头提
states”可知,此处指人们观察(observe)到的情况。
出这些问题是为介绍新的发明作铺垫。
3.A 根据空前的“astrangefireball”可知,此处应是指不明
6.C 细节理解题。根据第二段中的“theHelrnfonisa big
飞行物划过天空燃烧(burn)。
helmet... giving the wearers their own quiet personal
4.A 根据上文描述可知,此处指数千人观察到的现象,
space”可知,头盎给佩戴者提供了一个安静的个人空间。
sighting“看见,发现(尤指罕见的或短暂出现的事物)”符
7. D 细节理解题。根据第四段中的“Theonlytrouble is
合语境。
that it makes you look like a character... even Native
Americanheadgear”可知,这种头的劣势是它的外观看
5.C 根据第一段中的“raced across the US and crashed near
起来很奇怪。
Kecksburg”可知,这个小镇与这个事件联系(connect)最为
8.B 推理判断题。根据最后一段的内容可知,这家公司目
紧密。
前正在努力改善头盛的设计,并计划在市场上销售。
6. D 根据下文中的“she saw strange blue thin lines of fire
II. [语篇解读] 文章讲述了 ScottKelly起初对科学并不
risingfromthe trees”可知,事件应发生在树林(wood)里。
感兴趣,但是找到了人生目标后,他开始努力学习科学,最终
7.B 此处表示一个小男孩的母亲向当局报告(report)。
实现了成为字航员的目标。
8.A 根据语境可知,人们查看现场时无意中发现(come
1.C 根据语境可知,此处指Scott对科学和其他所有学科都
across)一个奇怪的橡实形状的、有一辆小汽车大小的
不感兴趣,故C项符合语境。
物体。
2. D 由上文中的“he was absent-minded and uninterested in
science and all other
aswell”可知,Scott总是心不
9.C 本文描述的是一个神秘的事件,因此上面的文字也应
在焉,对科学和其他所有学科都不感兴趣,故此处应是指
是奇怪的(strange)。
他无法集中注意力听老师讲课。focuson“集中注意力
10.D 根据语境可知,一支军队驻守(presence)在坠毁现场,
于......”符合语境,故选D。
军官命令(order)普通人离开现场。
3.B 根据上文描述可知,ScottKelly对科学不感兴趣,无法
11.C 参见上题解析。
把注意力集中在老师讲的内容上,再结合下文中的“he
would never
12.A 根据语境可知,此处指确切地说(exactly),50多年前
his dreams"和“After so many years
坠毁在那里的是什么东西依然是个谜。
of daydreaming”可知,此处指他在学校大部分时间都在空
13.B 根据语境可知,这个神秘事件仍然饱受争议和争论
想。故选B。
4. A 根据下文中的“barely graduated from high school"可
(debate)。
知,Scott勉强才从高中毕业,故可推知,此处指Scott的成
14.A 根据语境可知,甚至有人认为那个物体(object)是外
绩很糟糕,故选A。
星人访问的证据。文中多处出现的object是提示信息。
5.C 根据上文描述可知,Scott的成绩很差,勉强才从高中
15.A 根据语境可知,此处表示无论是什么情况(case),发
毕业,故此处指他甚至认为自己永远也实现不了自己的梦
生在凯克斯伯格的神秘事件还会持续很多年。
想。故选C。