＂be+不定式＂表虚拟语气

即用于与事实相反的虚拟条件句，表示虚拟语气。此时be通常要用were这一形式，但在非正式文体中也可用was。如：

I’d be sorry if you were to think that I disliked you. 若是你认为我不喜欢你，那我就太伤心了。

If it were to rain, we would have to cancel the match tomorrow. 假如下雨, 我们只好取消明天的比赛。

注意其省略倒装形式：

If I were to tell you / Were I to tell you that I killed him, would you believe me? 假如我对你说是我杀死了他, 你相信吗?

If I were to do that / Were I to do that, what would you say? 如果我做了那件事，你会说什么呢?