Question

 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．ours1

Answer 1

B。

that在此用于引导宾语从句，用作动词check的宾语。句中的现在分词having checked带有两个宾语从句 (that) the doors were closed和that all the lights were off，只是前面一个宾语从句省略了引导词that。