They happened to _____ for Tianjin when we got there. A.leave B. have left C.leaving D. had left
问题描述：
They happened to _____ for Tianjin when we got there. A.leave B. have left C.leaving D. had left
答案是B,求解释为什么不填A,词组中不是应该用原型吗?
答
to do sth.这是常见的不定式后跟动词原形,表即将发生、未发生的事情.若表达已经发生的事情,用 to have done sth.结构题中,当我们到达那里时,他们碰巧已经离开去天津.我们到时,他们已经离开,离开的动作在我们到达时就...