when will you return to china?答案是not until next week ,为什么不能用after a few weeks?

题目

when will you return to china?答案是not until next week ,为什么不能用after a few weeks?

答案

因为问句是用一般将来时,如果用after则需是一般过去式的,after是描述过去某一时间段中的以后,not until next week直到下星期才回很明显是将来的时间,所以是not until next week.