请大家帮帮忙啊。。。这个问题颠覆了我对现在完成时的理解。。

萧尧

10、Carnivorous mammals can endure what would
otherwise be lethal levels of body heat because they
have a heat-exchangenetworkwhich kept the brain
from getting too hot.

which kept

that keeps

which has kept

that has been keeping

having kept

A Kept is the wrong tense.
B Correct. The verb keeps indicates a current
situation and is consistent with the other
verbs in the sentence. The sentence is clear
and concise.
C Mistaken shift in tense: In this sentence the
present tense expresses a timeless general
principle; in contrast, has kept indicates a
more definite context and time period and
suggests that the heat-exchangenetwork
mayno longer have this effect.
D Has been keeping is the wrong tense.
我理解的现在完成时是：过去发生，持续到现在，并且对现在产生影响。可是与C的红字说法部分相悖啊。大家给我解答一下好不好？

fanaf821

我记得manhattan上面说 现在完成时是过去的动作延续到现在或者其影响持续到现在 我觉得c的意思是说 选项c中的现完相对于选项a中的一般现在时 表达了动作可能已经结束的不确定性（也就是第二种情况：它的影响持续到现在）所以a中的一般现在时对于客观事实更好的刻画 使得a is better than c

dreamistrue

which应该用非限定性修饰吧，所以不对。描述的是一个客观事实，不需要用完成时，用一般现在时就可以解释清楚了啊。

arielchung

manhattan 说：完成时
1. 动作开始于过去，动作延续到现在，还在继续
2.动作结束了，但是动作的结果对现在还有影响

c的解释，应该是指2。完成时要根据上下文来诠释。这道题，由于是客观事实，lz不要纠结了。

当时看到这个解释的时候，我也忧郁了一下。不过不要紧。当个特例记着就好了。