Question

形容词后的to都是介词吗?给个确切的答案

Answer 1

不是的.

to有两种情况,含有to的短语里面：

1.是固定搭配,既不能用其他的短语代替想表达的意思的：

look forward to(prep.)+doing something期待某事

set down to doing something开始着手某事

2.可以替代的：

want to do something=would like to do something

have to do something与need to do something意思相近.

to是介词情况的短语还是需要靠记忆.