=______．
参考答案：[*]
解析：
[分析]： [*] 而[*] 所以原式[*]
You should be careful when you see the sign . It means "Danger".
If you go to America, you will find that there are better（）by road, rail and air than in London.
A.transport
B.traffic
C.communications
D.vehicle
=______．
=______．