at what time will he 为什么前面要加个at

题目

at what time will he 为什么前面要加个at
不加at 又成什么了

答案

什么时候他将离开.at what time=when
表示“在.时候（几点）”用"at."
eg.I get up at 6:00 every day .
He often goes to school at 7:00 in the morning.