斜Y形坡口对接裂纹实验适合于（）焊接接头
A、不锈钢
B、碳素钢
C、铸铁
D、低合金钢
参考答案：B, D
I like Tianjin because it is my home town and it's also one of _____ China. [ ]
A. the cities
B. the big cities
C. the biggest
D. the biggest cities
在规范的分类中，社会规范不包括( )。
A．技术规范 B．社会团体规范C．法律规范 D．道德规范
