响墩的放置，其间距为多少米？
参考答案：响墩的放置，其间距为20米。
Speaker A: Do you mind if I sit down hereSpeaker B: ______
A．Of course. Do sit down, please.
B．Not at all. There's plenty of room.
C．Never mind. I'd like to have some companion.
D．Sure, I'd like to have somebody to talk to.
什么是水资源？水资源的经济学特征有哪些？
