On tank vessels equipped with power operated cargo tank valves, the type of power operator most commonly used is （）.

单项选择题When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, you should （）.

A.increase the amount of cooling water to the condenser
B.decrease the amount of cooling water to the condenser
C.add more refrigerant to the system
D.remove some refrigerant from the system

单项选择题Which of the following statements is correct concerning heat transfer?（）

A.Heat is given off from a high temperature region known as a heat sink
B.Heat transfer rate is affected most by the size of the heat sink involved
C.Heat transfer rate is affected most by the temperature difference between the heat source and the heat sink
D.Heat transfer by radiation will occur only by mass motion of a fluid substance

单项选择题Who is responsible for ensuring that someone is assigned to close the watertight doors in an emergency?（）

A.Maritime Safety Administration
B.Master of the vessel
C.Chief Engineer
D.Chief Mate

单项选择题The rate of heat transfer from a hot region to a cold region is affected most by the （）.

A.size of the heat sink
B.temperature difference between the regions
C.size of the heat source
D.total heat of the system

单项选择题A gradual decrease in the discharge pressure of an operating hydraulic pump can be caused by （）.

A.the four-way control valve failing to shift
B.the bleeder valve sticking in the open position
C.cold hydraulic fluid
D.a clogged air vent falter on the oil reservoir