. Sales of CDs have greatly increased since the early 1990s, when people to enjoy the adv

发布时间：2020-08-17 12:44:55

. Sales of CDs have greatly increased since the early 1990s, when people      to enjoy the advantages of this new technology.
A. begin
B. began
C. have begun
D. had begun

网友回答

A. begin
(答案→)B. began
C. have begun
D. had begun
解析：  when引导的是一个非限制性定语从句，when指20世纪90年代初，当然用一般过去时。
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