判断齿轮泵转向的依据是（）
A.原动机转向
B.安全阀的位置
C.吸排口方向
D.齿轮啮合状况
参考答案：A
--- Was it by cutting down staff _ _she saved the firm?
----- No, it was by improving work efficiency.
A．when
B．what
C．how
D．that
ng氧气里有m个氧原子，由此可推出阿伏加德罗常数为（）。
A.16m/n
B.32m/n
C.16m/nmol-1
D.32m/nmol-1
