He studies by doing a lot of exercises for a test.(就画线部分提问)

问题描述:

He studies by doing a lot of exercises for a test.(就画线部分提问)

你这划线部分在哪啊?要是画的He,就是who studies by doing a lot of exercises for a text?如果是 doing a lot of exercises 就是By what does he study for a test?如果是for a test就是Why does he study by doing...