解释keep to 和a waste of time 和be short of 并分别造句

解释keep to 和a waste of time 和be short of 并分别造句 be waste of 和be a waste of区别 用“a waste of time”造句. 怎么用a waste of time造句 a waste of time 怎么造句? a waste of time 咋个造句 a waste of time most of it being a complete waste of time,but needs to be do No one would be a waste of time to understand me.Cruel ..这句话 be taken a waste of time 是固定用法吗? run short of和be short of有什么区别 用be short of造句