Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.

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

The control mode in which the final control element is moved from one of two flexed positions to the other is known as （）.

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

The temperature differential occurring between the inlet temperature of the fluid to be cooled and the outlet temperature of the cooling medium in a shell-and-tube heat exchanger is greatest in which of the flow designs listed?（）

Thermostatic expansion valves can be adjusted for （）.

Heavy wear in a particular area of the inner circumference of a packing ring may be caused by （）.

If the thermal bulb of an expansion valve is incorrectly placed at the center of the coil instead of the end, it will （）.

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

When the steering gear is in operation, you should （）.