OGsc 12

绝望的小老鼠

Carnivorous mammals can endure what would

otherwise be lethal levels of body heat because they

have a heat-exchange network which kept the brain

from getting too hot.

(A) which kept

(B) that keeps

(C) which has kept

(D) that has been keeping

(E) having kept

OA：B
C的时态不对，OG解释说 has kept indicates amoredefinite'context and time period and
suggests that the heat-exchange network
may no longer have thiseffect.

为什么完成时态不是表示还在延续，而是暗示不再有效果了呢？

joymumu

现在完成时表示动作延续到现在或者动作的影响延续到现在，有可能会延续下去。这就限定了一个时间段。
而本句是要表达a timeless general principle，用一般现在时的话就没有限制时间段啦，表明这是个principle~


浅见哈~~~~~~~~~~

kiwifoodtown

现在完成时态是指事件发展到目前为止，不代表会继续发展，而一般现在时，表示一个常态，特别是在表述一个科学事实或客观真理时要用一般现在时。

绝望的小老鼠

谢谢joy，谢谢kiwi，  我明白了~~