根据《环境空气质量标准》(GB 3095—1996)的规定,CO的日平均二级标准限值为( ) mg/m3。
A.4 B.6 C.8 D.10
参考答案:A
---Jack was late for Mr. Smith’s oral class this morning.
---______? As far as I know, he never came late to class.
A.How come
B.So what
C.Why not
D.What for
如何理解网络安全策略中的物理安全策略?