单项选择题
Lube oil pumps taking suction from the sump of most small marine engines are usually （）.
A.of the diaphragm type B.of the centrifugal type C.of the positive displacement type D.independently driven by electric motors
单项选择题 Fuel oil begins injection into the cylinder of a four-stroke/cycle diesel engine during the （）.
单项选择题 Telescopic pipes to the piston of a large slow-speed main propulsion diesel engine are designed to prevent （）.
单项选择题 The water in an auxiliary boiler should be tested daily for （）.
