题干
— What is he doing?
— He ________ his MP4.
A：is listening
B：is listening to
C：listening
D：listening to
答案(点此获取答案解析）
B
— What is he doing?
— He ________ his MP4.
A：is listening
B：is listening to
C：listening
D：listening to
和cL水蒸气（温度.压强与原混合气相同），若a∶b∶c＝3∶6∶4，则下列叙述中正确的是( )
