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

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

Which of the following statements is correct concerning heat transfer?（）

If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.

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

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

The output volume of a positive fixed displacement pump can be changed only by （）.

If the viscosity of the liquid being transferred remains constant as the discharge pressure increases, the rotary pump （）.

Thermostatic expansion valves can be adjusted for （）.

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?（）