Question

The students ________ busily when Miss Brown went to get a book she ______ in the office.

A．had written, left　　　　　B．were writing, has left

C．had written, had left　　　D．were writing, had left

Answer 1

D

解析:

“把书忘在办公室”发生在“去取书”这一过去的动作之前，因此忘了书这一动作发生在过去的过去，用过去完成时。句中when表示的是时间的一点，表示在“同学们正忙于……”这一背景下，when所引导的动作发生。因此前一句应用过去进行时。