back before nine o’clock.
问题描述：
back before nine o’clock.
---Mum,I’m outing.
---Well,and ____ you play or go shopping,you must come back before
nine o’clock.
A.whenever B.whether C.whichever D.no matter
为什么不能选D
答
whether…… + 祈使句,固定结构,“不管……,一定要……”为什么不能选D可以，但是也要交whether，如： No matter whether it is light or dark at that hour, we've decided to leave at five o'clock in the morning. 不管到时候是否天亮，我们都已决定早晨5点离开。