题干
— What are Mary and Helen in the room now？
— They are listening to music.
A：does；both
B：doing；all
C：doing；both
答案(点此获取答案解析）
C
— What are Mary and Helen in the room now？
— They are listening to music.
A：does；both
B：doing；all
C：doing；both
和8mol
在一定条件下反应，达到平衡时，