2. 职称英语
  3. An adult giraffe’s head is about six feet above its heart. This means that to 【C

An adult giraffe’s head is about six feet above its heart. This means that to 【C

游客2023-07-17  40
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. [br] 【C4】
选项 A、half
B、multiple
C、double
D、pair
答案 C
解析 词义辨析题，根据空格前面句子意思可知，空格处应该是一个表示倍数的词，double名词表示“两倍”，符合句意，所以选C，前面提到长颈鹿的血压很高，所以排除A；multiple只是指“倍数，若干”，但是没有说明是多少倍，所以排除
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