除含铁(Fe)和碳(C)外,还含有其它元素的钢就是合金钢。()
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Information about the current foreign markets () very important to our company.
A. is
B. was
C. are
D. were
直径小于()的管道,可以直接关闭煤气阀门,切断气源灭火。
A. 80mm
B. 100mm
C. 150mm
在供电设施上发生事故引起的法律责任,按供电设施产权归属确定。
A. 正确
B. 错误
The boiling and condensation points of refrigerant mainly depend on the () exerted upon it.
A. temperature
B. density
C. volume
D. pressure