单项选择题
The lifting pressure of （） is set in the presence of a Surveyor it is locked and cannot be changed.
A.fuel valves of main engine B.injector pump of main engine C.safety valves of marine boiler D.safety valves of a reciprocating pump
单项选择题 The propeller is pushed on to the tubeshaft taper and made tight by（）
单项选择题 For a propeller direct driven by the engine,（）.
单项选择题 Propeller running at （） are generally efficient.
