where were you that time?was dinner ready at that time?为什么都是时间状语,但却一个加at,一个不加

题目

where were you that time?was dinner ready at that time?为什么都是时间状语,但却一个加at,一个不加

答案

At that time 强调时间点或时刻
that time 可以表达那个时期或时代