difficult to加什么词?

be difficult后加什么? much difficult than前面加什么is? prove difficult 和 prove to be difficult 有什么区别? difficult是加动词ing?还是加to do sth. difficult 后加doing还是加to do it is difficult to see什么意思 Very difficult to understand什么意思 to后加什么词 difficult for sb to do sth 和difficult for sb doing sth 有什么区别 She felt it difficult to walk.此句中的difficult作什么成分? He found difficult to be a top student.填什么? It's difficult to love everyone什么意思