We had a very difficult time ______ some of the problems 选项:a、discussing b、to discuss c、to kn
问题描述：
We had a very difficult time ______ some of the problems 选项:a、discussing b、to discuss c、to kn
答
a
答
b
答
have+ 宾语+宾语补足语
have a very difficult time （in）doing sth
所以用discussing 表示已发生的情况.