Do you have any idea when that was caried out?
问题描述：
Do you have any idea when that was caried out?
It was not until last year _______ their plan was approved.
A.whenB.that
答案是A还是B,为什么?
答
when
last year 是个时间 that 通常都能用,代人、地点、时间等,这里用when更确切~