当加工细长轴零件时,必须附加辅助支承()。
A.中心架或跟刀架
B.鸡心夹头
C.花盘
D.顶尖
参考答案:A
The writer is not satisfied with _______ buses are too crowded.
A.that
B.which
C.what
D.the fact that
在化学反应2A+B2=2AB中,A 与B2反应的质量关系如右图所示,若6g A和8g B2充分反应,则生成AB的质量为
A.9g
B.11g
C.12g
D.14g