是的,一定要用原形 .后面的那个是介词后面的动词.还有许多是动词短语的固定搭配.
有的跟原形,有的跟to do .有的跟doing .
B ,have fun (in) doing sth.愉快的干某事 ,类似的还有
have problem (in ) doing sth.
have trouble (in ) doing sth.
have difficulty (in) doing sth.
want to do sth.finish doing sth .