it is not long before they are so accustomed to swimming.急

问题描述:

it is not long before they are so accustomed to swimming.急
it is not long before they are so accustomed to swimming 这里to后面的swim怎么可以用ing形式呢?

It is not long before they are so accustomed to swimming.
没用多久他们就对游泳习以为常了.
be accustomed to (doing)sth,习惯于做某事
这里的to并不是不定式,而是介词,在介词后的动词要变为动名词,做介词的宾语.