is often the case with human beings, many animals sleep a lot when young, but sleep much

is often the case with human beings, many animals sleep a lot when young, but sleep much less when they get older.
A. Which
B. What
C. As
D. That

A. WhichB. What(答案→)C. AsD. That解析：C 考察定语从句，句义：和人类一样，很多动物在年幼睡觉时间多，长大以后就睡得少了。引导非限制性定语从句时候，as可以放在句首，或者主语之后，which不放在句首，BD两项不能指代全局。故C正确。

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