首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
How does a whale keep itself warm?
How does a whale keep itself warm?
admin
2014-03-25
52
问题
How does a whale keep itself warm?
Millions of years ago, whales lived on land and walked on four legs. Today, whales still have small bones that are the remains of their hind legs, but these bones can only be seen on the inside of the whale. No one knows why whales left the land to live in the water.
However, scientists can imagine that when the whales changed their environment, their bodies underwent a change—taking on a more fish-like appearance. This new form offered less resistance to the water, enabling the whales to swim faster.
Despite their fish like form, whales are not fish. A whale will drown, just as a man will, if it stays under water too long. When a whale is under water, it closes its nostrils tightly and holds its breath. The air in its lungs becomes very hot and full of water vapor. When the whale rises to the surface and exhales, its hot breath produces a column of water vapor that rises high in the air. A man produces the same effect when he exhales warm air on a cold morning.
Whales are classified as mammals because they bear their young, rather than laying eggs, and because the mother whales give the babies milk. Like other mammals, whales have warm blood. Their blood stays at the same temperature, even when they move from hot to cold water. They keep warm in cold water because they have a thick layer of fat just under their skins. This fat is called blubber, and it is thicker on whales that spend their lives in cold water. Almost all land mammals, except man, have hair on their bodies to keep them warm, but whales, which have very few hairs, are kept warm by their fat.
选项
A、They have very few hairs on their bodies.
B、They bear their young rather than laying eggs.
C、Their lungs are full of hot air and water.
D、They can walk on their hind legs on land.
答案
A
解析
转载请注明原文地址:https://kaotiyun.com/show/spxd777K
本试题收录于:
公共英语四级笔试题库公共英语(PETS)分类
0
公共英语四级笔试
公共英语(PETS)
相关试题推荐
Whatisanimportantgoalforsomedevelopingcountries?
What’sthepossiblerelationshipofthetwospeakers?
Intherelationshipofeducationtobusinessweobservetodayafinestateofparadox.Ontheonehand,theemphasiswhichmost
WhichofthefollowingiscoveredinBCDInternationalprograms?
Whatcoursearethespeakerstalkingabout?
Asidefrom.perpetuatingitself,thesolepurposeoftheAmericanAcademyandInstituteofArtsandLettersisto"foster,assis
WhydomanypeoplecriticizeTVprogramsintheU.S.?
Moviegoersmaythinkhistoryisrepeatingitselfthisweekend.Thesummer’smostanticipatedfilm,PearlHarbor,whichhasopene
Howdoesawhalekeepitselfwarm?
WhyisLauraatthebicycleshop?
随机试题
甲建设单位与乙设计院签订设计合同,设计费用为300万元,双方在协商定金数额时发生意见分歧。根据《担保法》的规定,该定金数额最多为()万元。
ERP在会计电算化中指()。
保税加工货物内销征税,下列需要征收缓税利息的是()。
与用益物权比较,担保物权的特征有()。
公文附件的顺序和名称应标注在()。
2007年末全国总人口为132129万人,比上年末增加681万人。全年农村居民人均纯收入4140元,扣除价格上涨因素,比上年实际增长9.5%;城镇居民人均可支配收入13786元,扣除价格上涨因素,比上年实际增长12.2%。按农村绝对贫困人口标准低于785元
美国最长的河流是:__________
山西醋产业协会某前副会长称,在市面上销售的山西老陈醋中,只5%是不加添加剂的真正意义上的山西老陈醋。中国调味品协会某副会长就此事件接受记者采访时说:“只要按国家标准加添加剂,就没有安全问题。有些企业强调自己未加添加剂,这对按正常标准加添加剂的企业来说是不公
项目管理中,主要是对(19)________4个变量的控制。
InJapan,mostpeoplestillfeelthatawoman’splaceisinthehome;andmostwomenwillinglyaccepttheir【C1】______roleaswif
最新回复
(
0
)