等离子弧焊必须对电极及喷嘴进行有效的水冷却,冷却水的流量不得小于( )。
A.2 L/min
B.3 L/min
C.6 L/min
D.8 L/min
参考答案:B
The reason ________ he didn’t come was _______ he was ill.
A.why; that
B.that; why
C.for that; that
D.for which; what
1991年,公安部对人民警察的职业道德规范进行了全面系统的概括和阐述,并在全国公安系统颁布施行《人民警察职业道德规范》。 ( )