have difficulty还是difficultyies (in)doing sth?

问题描述:

have difficulty还是difficultyies (in)doing sth?
老师讲师可数,补习书上特意讲的是不可数 到底可不可数啊
统一一下啊、

difficulty本身是可数名词.
但在have difficulty(in)doing这个句式中一般是用单数的.