如图所示，桌面上有两只空啤酒瓶，一只竖直放在桌面上，另一只放倒后平放在桌面上．用力对着它们吹气，会发现：能吹动右侧的啤酒瓶，但不能吹动左侧的啤酒瓶．这表明在压力相同的条件下，____ 　　．

氧化汞受热分解生成汞和氧气的反应前后，发生改变的是（　　）

阅读对话，根据对话选择正确的答案。

Zoom: Welcome to our school.

Monkey: Thank you.

Zoom: That is our playground. This is our new gym. We can play ping-pong in it.

Monkey: Is this your computer room?

Zoom: Yes. It's on the second floor.

Monkey: Do you have a music room?

Zoom: Yes, we do. It's on the first floor. This way, please.