∵2:3=x:4,
∴23=x4,
∴3x=8,
x=83,
故选B.
You have never been to Bridge Street, _____? [ ]
A. have you
B. haven't you
C. do you
D. don't you
煤烟型烟雾事件的主要污染物是()。
A.SO2和颗粒物
B.NOx
C.SO3
D.汽车尾气
E.O3和颗粒物