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
题目分析：这几个选项exist所用的时态不一样，有的用过去完成时，有的用过去式，如果用过去完成时表达的意思就是exist这个动作应该发生在led之前了，表达的语义逻辑不对，干掉A，D。B用in what are now C用where there were ，C明显意思说的费劲，E中的now that后面又出现了个are，那when后面到底是existed是谓语还是are是谓语，乱七八糟的，选B。
