冰川世纪的模糊问题~

In OG 11th

59. 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* concept of an age in which great ice sheets' had existed in now currently temperate areas.

A) in which great ice sheets had existed: 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

OG对C的解释有一点：“where there were areas now temperate”is wordy and confusing。

我怎么看不出来这有什么confusing的呢？

OG对D的解释有一点：“in current temperate areas ”is unclear。

我也没看出来这个部分怎么不清晰了……

因为NN们都说OG要研究得彻底一点，所以，呵呵，我就提出这样小小的问题了~对于这种OG说模糊的地方，我还真是常常雾水一片呢~请大家帮帮忙指点迷津噢~

where 在这里修饰什么呢？ 没有先行词

OG对D的解释有一点：“in current temperate areas ”is unclear。

新东方的解释是，表现在怎么样只用 what is/are now