问题
选择题
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
答案
答案：D
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”。