单项选择题
（）, remedies must be taken to stop it as early as possible.
A.Any surge occurs B.Any surge occurred C.Should any surge occur D.Should any surge occurring
单项选择题 （）, the motion would continue indefinitely once it had started.
单项选择题 （） the bodies are, （） the friction will be.
单项选择题 Convection is the principal means （） temperature is equilibrated in liquids and gases.
