对于均质流体,其体积为V,质量为m,则密度ρ=()。
A.m/V
B.mv2
C.m•V
D.V/m
参考答案:A
We were told whether _____ a Christmas party was still under discussion. [ ]
A. to hold
B. holding
C. hold
D. held
真空泵的安全操作要点包括()。
A.防止负压吸入空气引发爆炸
B.有章不循,违章作业
C.防止静电引起燃烧
D.尽可能使用液环式真空泵