题目
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.
【C1】
A.bring
B.produce
C.transfer
D.pump
第1题
He has a very adult manner although he’s only 12.(英译汉)
第2题
The author feels that as au adult one must ______.
A.achieve one's ambitious at all costs
B.continue to be ambitious
C.find a compromise between ambition and reality
D.give up all one's earlier ambitious
第3题
第4题
第6题
第7题
As an adult, I still love reading children ’s books. I like the works published by() press.
A、juvenilia
B、juvenile
C、youthful
D、young
第8题
45 is belong to () at the stages in a person's life.
A、Young adult
B、Middle age
C、Mature
D、Senior
第9题
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