采集室外空气空白样品应与采集室内空气样品同步进行，地点宜选择在室外（）。
A.上风向处
B.下风向处
C.无风处
D.阴凉处
参考答案：A
— Excise me. Could you please tell me how I can get to the supermarket?
— Go straight and take the first turning on the left. You can't miss it.
Which of the following is the right way to the supermarket? [ ]
A. B. C.
共同配送的主体必须是货主，这样可以在不增加物流成本的前提下，实现小批量、多批次配送。
B. 
C. 