单项选择题
What will NOT increase friction of a liquid flowing in a pipe and cause a loss of suction head?（）.
A.Bends in the piping B.Slowing the pumping rate C.Pipeline valves D.Backing rings for pipe welds
单项选择题 What normally helps in detecting escaping gas? （）
单项选择题 What is used to test a tank for oxygen content?（）
单项选择题 What is the proper first aid for LPG in the eye? （）
