问题补充：
If they what I was saying, they’d know what I was talking about.
A. took the trouble to listen to
B. had trouble listening to
C. take the trouble to listen to
D. have trouble listening to
答案：
(答案→)A. took the trouble to listen to
B. had trouble listening to
C. take the trouble to listen to
D. have trouble listening to
解析：考查与现在相反的虚拟语气，从句用：if + 主语+ 过去式/were,主句用：would/could/might do,句意：如果他们努力听我所说的话，他们会明白我谈论的是什么。短语：take the trouble to do 不辞辛苦做某事，非常努力做某事。所以选A。
