OG 59（exist的过去完成时）

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

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

Verb form

In which or when can be used interchangeably in this sentence. The verb form here should be the simple past existed rather than the past perfect had existed. Now currently is redundant because both adverbs express the same idea.

有两个问题。

1. 不用had existed是否是因为在这里如果使用过去完成时，就暗示“现在已经不存在了”。但题目并没有表达这个意思，所以用 existed这个时态更好。我做题受到1837这个时间的影响，认为是过去的过去。

2. existed in "what are now temperate areas" 是个what引导的什么从句？对what引导的从句总是有点糊涂。这里"what are now temperate areas"改为“now temperat areas” 或者“currently temperat areas”是否也正确？

请大N们指教。

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

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

是的，能看到非正确选项的错误点。但除了作对题目，我还想了解大家对我提得问题的看法？另外，答案确实有根据"had existed"来排除选项的。谢谢