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. ours1
答案:
A. why
(答案→)B. that
C. when
D. ours1
解析: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。