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
网友回答
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。