The problem is not easy_____.A.to explain B.to be explain C.explaining D.explained 请解释为什么选你所选的答案.
问题描述：
The problem is not easy_____.
A.to explain
B.to be explain
C.explaining
D.explained
请解释为什么选你所选的答案.
答
A.It is not easy to explain this problem=The problem is not easy to explain
答
A
在这种结构中to之后explain的宾语是很明确的（就是PROBLEM）
所以用主动就行了