题目内容：

They didn't know _____their holiday?
A,how they can spend
B,how could they spend
C,how to spend
D,how they will
要说明原因噢,为什么?B怎么不对

优质解答

这是宾语从句,要注意连接词、时态、语序三要素.
因为主句是didn't know过去时,所以宾语从句要用过去的时态,AD 不正确
B could they 这个语序是疑问语序,如果改成 they could 就对了
C 是不定式短语,可以放在疑问词后面使用