Traffic is becoming worse and worse in big cities. Heavy traffic has caused a lot of      to people’s life and work. For example, people have to get up      to go to work on time and come back very late when their work is     .

There are many causes (原因) for      problems, but the following may be the most important ones. One cause is the great increase (增长) in the         of private cars. Cars need more space but they      fewer people. When more and more cars appear, roads and streets become very     . It also causes air pollution. The other cause is that some people don’t care about traffic     . They cross the streets even when the traffic lights are still     . This may easily cause traffic accidents. But how can we      these problems? I think if we go out by bus or by bike more often, we’ll use cars less. It may be a helpful way.

某地一民用建筑中，占地面积2000m²，顶棚表面局部采用泡沫状塑料，现对其进行装修，装修涂料选用防火涂料。住宅隔墙间设防火墙，内部装修设有安全出口，疏散出口等，楼道内装有自动灭火系统。

当胶合板表面涂覆一级饰面型防火涂料时，可作为( )级装修材料使用。

A．A

B．B₁

C．B₂

D．B₃