885 sec14-13

13.   His studies of ice-polished rocks in his Alpine homeland, far outside the range of present-day glaciers, led Louis Agassiz in 1837 to propose the concept of an age in which great ice sheets had existed in now currently temperate areas.

(A) in which great ice sheets had existed in now currently temperate areas

(B) in which great ice sheets existed in what are now temperate areas

(C) when great ice sheets existed where there were areas now temperate

(D) when great ice sheets had existed in current temperate areas（B）

(E) when great ice sheets existed in areas now that are temperate

关于这道题，以前也有讨论过

但是我还是没有明白为什么B比A好，一个是关于时态，

题目中不时有一个过去的时间点（1837）了，用过去完成时不好吗？

还有，in what are now temperate areas为什么比A中的关于地点的表达方式好啊？

这里exist没有要表达过去的过去，对现在而言只是过去，所以不用过去完成。

A中主要是now currently重复。