a waste of 是词组吗,那是什么意思?还是waste是可数名词

a waste of 后面是接可数名词还是不可数名词? Waste 做名词时是可数名词还是不可数名词? 请问waste作名词到底是可数还是不可数的 waste是不可数名词吗 是pollute waste 还是polluted waste?为什么? waste的用法是waste in还是waste on waste修饰名词要加of吗 例如a waste of time be taken a waste of time 是固定用法吗? 短语a waste of time 后加的是 to do还是 doing? a waste of time后面是加 doing sth还是to do sth 是It is a waste of time to play computer games 还是Playing comp a waste of time