单项选择题
A.pressure does not fluctuate rapidly
B.pressure remains steady and unchanged
C.brine density does not exceed 1~5
D.brine density is too low
单项选择题 In most pumps and pump motors overpacking the ball bearings full of grease will result in （）
单项选择题 Aqueous Film Forming Foam (AFFF), commonly known as ‘light water’, is especially suitable for fighting （）
单项选择题 Which of the following statements concerning the water tube and fire tube boilers is not true?（）