he practices playing the piano every daay为什么play要加ing而 I see

he practices playing the piano every daay为什么play要加ing而 I see he practices playing the piano every daay为什么play要加ing she practices（）（play）the piano every day.为什么填playing he practices playing the piano every day对ev I practise playing the piano中“playing”为什么要加ing? I love playing the piano 我喜欢弹钢琴. play后为什么要加ing? 希望能解释的详细一点.谢 The little boy practices playing the piano every day I often see him practices playing the piano改成被动语态 I like playing volleyball为什么play要加ing? he teaches us play the piano这个play要不要加ing 为什么Playing football.Play要加ing When is he going to play the piano?为什么加ING