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 what are now temperate areas
(A) in which great ice sheets had existed in what are now 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
I understand existed can't be compare with led but I think the part underlined is the content of the concept and this concept was proposed in 1837. Thus I believe it should use past perfect.
Also, the explanation of choice E on OG is "Now is an adverb and shouold be placed just after the verb are". Can I understand this like if I put now after are, this choice is right?
Thanks in advance!
(A) in which great ice sheets had existed in what are now 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
I understand existed can't be compare with led but I think the part underlined is the content of the concept and this concept was proposed in 1837. Thus I believe it should use past perfect.
Also, the explanation of choice E on OG is "Now is an adverb and shouold be placed just after the verb are". Can I understand this like if I put now after are, this choice is right?
Thanks in advance!
