我国现在实行省县乡三级制，如广宁是一个县。我国建立县制开始于[ ]
A．春秋
B．战国
C．秦朝
D．西汉
答案：B
发生高浓度瓦斯爆炸时，应该加大通风量，把瓦斯浓度降低到爆炸限以下。
Speaker A: How about the food I ordered I’ve been waiting for 20 minutes already. Speaker B: （）。
A. I’m very sorry, sir. I will be back with your order in a minute.
B. Ok. I will bring it to you in a moment.
C. Don’t worry. It will be ready soon.
D. Sorry, but I think you should have ordered it earlier.
