请问大全332

redemption

332.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
答案是B，用的是一般过去时，但是显然应该是在Louis Agassiz propose之前，他在1837年propose,所以是过去的过去，应该用过去完成时态吧？

tintin2003

过去完成的时态是表示过去有而现在没有,且句中exist的意思是要表示现在的存在,所以用had不合逻辑.