直接顶分为四类，即不稳定、中等稳定、稳定、坚硬四种类型
参考答案：对
When realizing they would be ___ of traffic jams or air pollution more people will choose public transportation.
A．victims
B．survivors
C．murderers
D．tutors
在高炉冶炼过程中对高炉渣有哪些要求？
