2. 外语
  3. An adult giraffe’s head is about six feet above its heart. This means that to 【C1】______ enough blood up to the brain the circul

An adult giraffe’s head is about six feet above its heart. This means that to 【C1】______ enough blood up to the brain the circul

admin2012-12-13  42
问题 An adult giraffe’s head is about six feet above its heart. This means that to 【C1】______ enough blood up to the brain the circulatory 【C2】______ must be strong enough to keep the blood at very high pressure.
Biologists have known for some time that giraffes solve this problem by having 【C3】______ high blood pressure, about 【C4】______ that of human beings. But an international team of biologists began to 【C5】______ about this. If giraffes have such high blood pressure, they should have a 【C6】______ problem with swelling in their legs and feet. Why don’t giraffes have swollen feet?
    Giraffes should have 【C7】______ problem, too. Every time they bend heads 【C8】______ to drink, the blood should 【C9】______ to their heads and have a hard time 【C10】______ back up (when the head is down) to the heart. How come giraffes don’t black out when they drink?
    The answer to the 【C11】______ feet problem, the researchers found, is that giraffes have 【C12】______ the researchers call a "natural anti-gravity suit". It 【C13】______ out that the skin and other 【C14】______ in their legs and feet are 【C15】______ stiffer and tougher than those of other 【C16】______ . As a result, the blood vessels in the leg cannot swell.
    Therefore, the blood has nowhere to go but back to the heart. What about blood rushing to the head 【C17】______ the giraffe bends down to drink? The researchers found that the giraffe’s jugular vein, which 【C18】______ blood from the head back to the heart, has lots of one-way valves in it. In the giraffe’s neck, there are lots of muscles that flex and relax repeatedly as the animal moves its head and sucks 【C19】______ drinking water. By squeezing the valved jugular vein, they 【C20】______ blood moving back to the heart even while the animal is drinking.
【C14】
选项 A、tissues
B、vessels
C、pores
D、organs
答案A
解析 词义辨析题，空格前的and说明空格处的词和skin并列，句意为“它们腿和脚上的皮肤和其他______”，tissue意为“组织”，符合句意，所以A正确，vessel意为“血管”，pore意为“小孔”，organ意为“器官”
转载请注明原文地址:https://kaotiyun.com/show/jCw7777K
0

大学英语四级

相关试题推荐
随机试题
最新回复(0)