对生态平衡不利的人类活动是（    ）

A: Hey, Cindy! Were you at home at 7：00 last night?

B: ____

A: Where were you then?

B: ____

A: The Music Club?  ____?

B: Oh, I played the violin there.

A:  ____?

B: I began to learn it at the age of 6.

A: I want to learn the violin too. Can you teach me?

B: ____

A: Thank you!