sad 后面接什么介词（sad过去形式是什么）

后边接介词to，例如：

1.It was sad to see them go.看着他们离去，真让人难过。

2.You'd have to be sad to wear a shirt like that.你穿着那样的衬衣显得老气。

3.We are very sad to hear that you are leaving.听说你要走了，我们十分难过。

4.He died five or six years ago I'm sad to say.很遗憾，他在五六年前去世了。

在英语里，这个单词后面加介词to，是固定搭配。