Question

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

Answer 1

B

本题考时态和句子结构。句中when是关系副词，引导定语从句，修饰the early 1990s。从句的意思是：当时（指in the early 1990s）人们开始喜欢这一新科技带来的好处。讲的是过去发生的事，与现在无关，排除A、C。从句中有表示过去具体时间的状语（when相当于in the early 1990s），不能用过去完成时。