【求解】I don't know___. A.when will they leave B.when they will leave C.when wouldthey leaveD.when they would leave 选B没错,但是为什么用陈述句语气呢?

【求解】I don't know___. A.when will they leave B.when they will leave C.when wouldthey leaveD.when they would leave 选B没错,但是为什么用陈述句语气呢?
【求解】I don't know___. A.when will they leave B.when they will leave C.when wouldthey leave
D.when they would leave 选B没错,但是为什么用陈述句语气呢?

【求解】I don't know___. A.when will they leave B.when they will leave C.when wouldthey leaveD.when they would leave 选B没错,但是为什么用陈述句语气呢?
when引导的时间状语从句,我不知道他们什么时候离开.他们什么时候离开 这一整个部分做句子的状语,是“我”不知道的内容.