单项选择题
When liquid is free to move transversely in a tank, the effect is called（）.
A.Free communication B.Free fensity C.Free surface D.Negative GM
单项选择题 When the truck does not work, the driver should（）engines.
单项选择题 When the vessel arrives, the cargo of machinery to be unloaded is（）.
单项选择题 When working with lumber, wire and staples are not desirable to be used because（）.
