Great efforts should be made to protect water resources if we___avoid water shortage.
问题描述：
Great efforts should be made to protect water resources if we___avoid water shortage.
A.are to
B.will
C.are going to
D.should
请解释一下各个选项的对错.
并说明一下be to do ,will ,be going to do 的区别
答
选D,这个应该是虚拟语气
be to do是打算计划做某事,be going to是将要做某事