Question

At home , he never seems to have time until after 10:30 p.m. ,_____his children have gone to bed.

At home , he never seems to have time until after 10:30 p.m. ,_____his children have gone to bed.
A whose time B when C on which D by which time
选什么，为什么？谢谢

Answer 1

D（错了表怪偶，好多年不做了）
因为是逗号隔开，而前面一句很显然是一个完整的句子，所以后面会跟一个从句。A很显然不对，连意思都不通；B的话就不要逗号了；C which后面少了time，而且介词貌似也有问题。
所以选D。