求助og上面的一点小迷惑

sgj

72. 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

为什么a选项的过去完成时是错的，是因为没有过去的时间点吗？1837不算吗？

renita12

看一下Ron大神的解释 很详细哦~

* first of all, studying verb tenses should be a low priority. verb tenses are VERY rarely tested alone -- i.e., they are usually tested in tandem with other errors, which can also be used to eliminate the choices -- so they aren't as important as more major topics, such as parallelism and pronouns.
there's also the fact that verb tenses are by far the most difficult aspect of any language for non-native speakers to learn. (this is not a fact about the english language in particular; this fact is true about any language in the whole world.) so, if you are not a native speaker of english, you will almost certainly derive a greater return on investment by putting your study time into other aspects of these sentences. this is doubly true because, as i said above, almost no problems require the use of verb tenses to get the right answer.

* regarding the perfect tenses (present perfect and past perfect):
the point of the perfect tenses is to stress one of two things:
* the completion of some action prior to the timeframe of the sentence, or
* the persistence of some state up to the timeframe of the sentence.
for instance, if i write by the time i arrived, all of the food had been eaten, i'm emphasizing the completion of this act -- it's all done; the food is all gone. if i write when i took him to the doctor, johnnie had already been sick for two weeks, the emphasis is not on the idea that johnnie was sick at the time of the sentence; the emphasis is on the fact that he had been sick for the previous two weeks -- a persistent condition.
this is the reason why “an age in which great ice sheets had existed” doesn't really make sense here. the emphasis of the sentence is on the fact that the ice sheets ACTUALLY EXISTED during this time. the sentence is not meant to emphasize the persistence of the ice sheets before that age, nor is it meant to suggest that the existence of the ice sheets was a completed action. therefore, the regular past tense is better.

again, i doubt that any of this will ever be required to solve one of these problems, but there you go.

Indigolove

this question has been transcribed incorrectly, sorry