发票邮寄费用是怎么算()
A、开票金额2000以上,商家承担
B、不用商家承担
C、开票金额2000以下,商家承担
D、开票金额2000以上,折800承担
参考答案:C, D
The air in mountain areas is ____ that in big cities.
A.as fresh as
B.fresher than
C.as dirty as
D.dirtier than
混凝土浇筑完毕后,应在()小时以内对混凝土加以覆盖并保湿养护。
A、12
B、24
C、48