Why hasn’t he come?________ on time, we would have to put off the trip.

A．If he doesn’t come

B．If he will not come

C．If he didn’t come

D．If he wouldn’t come

下面不属于对属性列和视图的操作权限的操作有（ ）。

A．建立索引

B．查询

C．插入

D．删除