最佳答案： 1.过去的情况： If we had found him earlier, we could have saved his life.要是我们当时早点找到他的话，我们就可以救活他。 →Had
1.过去的情况： If we had found him earlier, we could have saved his life.要是我们当时早点找到他的话，我们就可以救活他。 →Had we found him earlier, we could have saved his life.
2.现在或将来的情况： If she were here, she would attend the meeting too. 如果她在这里，她也参加会议。 →Were she here, she would attend the meeting too.
3.将来的情况： If it should rain tomorrow, we should have to stay at home.若明天下雨，我们只好呆在家里。 →Should it rain tomorrow, we should have to stay at home. 注意：若遇到否定词not时，不能与were/should/had缩略为Weren’t/Shouldn’t/Hadn’t而置于句首。 如：If I hadn’t warned you, you could have been killed. 正确：Had I not warned you, you could have been killed. 错误：Hadn’t I warned you, you could have been killed.
