had+过去式是什么时态
had + 过去式 = 过去完成时，例如
She had left when we visited her hometown.
我们在拜访她家时她已经离开了。
had
v.有;持有;占有;由…组成;显示出(性质、特征)；
aux.had 有时代替 if 用于从句句首，表示某种情况可能发生但并未发生；
have的过去分词和过去式
She\'ll have had the results by now.
她现在应该知道结果了。
We had a day out in the country.
我们在乡下玩了一天。
He had to go to the hospital for treatment.
Had I known that I would never have come.
要是早知道，我绝不会来的。
He had to go to hospital for treatment.
他不得不去医院接受治疗。