have problems 为什么要加doing

have problems/trouble doing sth 中problem为什么要加s have problem doing还是have problems doing? have problems in doing那为什么老师说have problem with speaking have no problems (in) doing sth.中的problem永远都加s吗? 为什么可以说have problems doing .problems是名词啊 名词后面怎么可以跟动名词啊 是不是可以h have problems doing sth与 have trouble doing sth have problems breathing中doing是什么 have problems to do,have problems doing sth,have problems wi have problems in doing 还是 have problem in doing 还是 have a pr have problems/trouble doing sth有什么区别 have problems doing的同义短语有哪些? have problems with to do sth 和doing sth 区别