They didn’t go to bed they finished their homework.A. whenB. becauseC. untilD. if

问题补充：

They didn’t go to bed they finished their homework.

A. when

B. because

C. until

D. if

答案：

A. when

B. because

(答案→)C. until

D. if

解析：句意：他们一直到完成他们的家庭作业才去睡觉。When当……时；because因为；until直到，常与not构成固定句型not···until直到……才； if如果。所以选C。