Having checked the doors were closed and all the lights were off the boy opened the do

问题补充：

Having checked the doors were closed , and all the lights were off, the boy opened the door to his bedroom.

A. why

B. that

C. when

D. where

答案：

A. why

(答案→)B. that

C. when

D. where

解析：主要测试宾语从句。该试题主要测试动词check后接宾语从句的情况，而且句中有并列连词and。句子意思：核实完所有的门已锁好，并且所有的灯已关好，男孩开门走进自己的卧室。