My mother wants to know——lunch with us tomorrow or not.I have no idea at the moment.But if
问题描述：
My mother wants to know——lunch with us tomorrow or not.I have no idea at the moment.But if
I——,I‘ll call you first.A.if you have ,am free B.whether you will have,am free C.if you have,will be free D.whether you have,wikk be free
答
很简单.
选B
whether ...or not 相比楼主老师教过的.据此排除A+C
剩下的if 从句当中 最不常出现的时态就是 将来时（will be free排除）
这样答案出来了.
纯手打的,楼主!