You can’t imagine what great trouble they have the problem .
A. to solve; being talked about
B. solving; discussing
C. to solve; to talk about
D. solving; being discussed
网友回答
A. to solve; being talked about
B. solving; discussing
C. to solve; to talk about
(答案→)D. solving; being discussed
解析：由have great trouble （in）doing sth.可知第一空应用solving; being discussed作定语修饰problem，表示“正在被讨论的问题”。