采煤机司机开机前必须先发出开机信号,停30秒钟后再开机。()
A. 正确
B. 错误
首次在中国销售的药品,在销售前或者进口时,指定药品检验机构进行检验。
A. 正确
B. 错误
液压传动系统中常用的管接头主要有焊接式、卡套式、扩口式和软管接头等。
A. 正确
B. 错误
The term "pour point" is defined as the lowest temperature at which lubricating oils will flow ().
A. rapidly
B. by gravity
C. through a standard orifice at a specified temperature
D. at a rate of 60cc per second