OG12--70

70.   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

Verb form; Rhetorical construction

In which or when can be used interchangeably in
this sentence. The verb form here should be the
simple past existed rather than the past perfect had
existed. Now currently is redundant because both
adverbs express the same idea.

A    Had existed should be existed; now currently is
redundant.

B    Correct. The simple past verb tense is

correctly used in this sentence; now is placed
and used correctly.

C     Where there were areas now temperate is wordy
and confusing.

D    Had existed should be existed; current should be
currently; in current temperate areas is unclear.

E    Now is an adverb and should be placed just
after the verb are.

The correct answer is B.

不是in what , 而是existed in+ what引导宾语从句

另外，选项B 本来就是simple past tense 不是past perfect tense

His studies……led LA to propose the concept of an age

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