下列各项与家鸽气囊功能无关的是（ ）
A：辅助肺进行双重呼吸
B：能进行气体交换
C：调节身体密度
D：能散热降温
下列生态系统中，有“绿色水库”之称的是（ ）
Steve's activity on Sunday
In the past
He spent most of the time 1.
He learnt it from his 2 and he is good at it.
Now
He spends at least 3 hours collecting rubbish.
He would like to protect the beach.
