the student always have fun singing English songs.为什么是singing
网友回答
singing English songs你可以当作状语,主语重复时可以动词ing形式充当状语,还原状语从句就是The student always have fun when he(she)sings English songs.
另外,如楼上所述,have fun doing sth.意思做某事很开心.
======以下答案可供参考======
供参考答案1:
HAVE FUN DOING STH 是固定的句子
供参考答案2:
have fun doing sth. 开心地做某事
没有have fun to do sth结构