单项选择题
The（）is fitted in the main steam supply line and is usually of the non-return type.
A.main steam stop valve B.auxiliary steam stop valve C.feed check or control valve D.blow down valve
单项选择题 The lifting pressure of （） is set in the presence of a Surveyor it is locked and cannot be changed.
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,（）.
