单项选择题
The valve best suited for throttling gas or liquid flow in a pipeline is the（）.
A.gate valve B.globe valve C.check valve D.plug cock
单项选择题 Which of the listed statements is a characteristic of the liquid charged power element used with thermostatic expansion valves?（）
单项选择题 Differential pressures can be measured with the use of a （）.
单项选择题 The function of a centrifugal pump double volute casing is to （）.
