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:

“把書忘在辦公室”發(fā)生在“去取書”這一過去的動作之前，因此忘了書這一動作發(fā)生在過去的過去，用過去完成時。句中when表示的是時間的一點，表示在“同學們正忙于……”這一背景下，when所引導的動作發(fā)生。因此前一句應用過去進行時。