单项选择题
The pipe friction and the resistance will （） as a result of an increase in the amount of fluid flowing through the system.
A.reduce B.rise C.raise D.fall
单项选择题 Air chambers are usually fitted to reciprocating pumps in order to （）.
单项选择题 Some pumps use packing as sealing glandThe gland should be （）.
单项选择题 Which of the following pumps is used where a relatively high pressure and small capacity are required?（）
