单项选择题
A.The profile of the valve is like a globe
B.The valve seat is set into the bulbous body
C.The plug or disc of the valve is made vertical to the axis of the pipe
D.The valve seat is located at right side of the plug or disc
单项选择题 Cocks and valves control or interrupt flow, and have internal passages arranged so that they can be restricted or closed: in cocks, by rotating the plug, and in valves, by lowering, raising or rotating a disc in relation to a seating surfaceAccording to the above sentence, which of the following statements is not true?（）
单项选择题 It should be apparent that little or nothing is gained by opening a drain at the same time as or after admitting steamThe above sentence probably means （）.
单项选择题 It is usual to identify the fluids in pipes by bands of paint at intervals, and the engineer should familiarize himself with the code in use.According to the above sentence, which of the following statements is true?（）