River currents tend to（）. ["Pick up speed where the channel widens","Run slower in the center of the channel","Hug the inside of a bend","Cause the greatest depth of water to be along the outside of a bend"]
When the refrigeration demand is small,（） ["the expansion valve will move toward the wide open position","the expansion valve will move toward the closing position","the feeler bulb will conveys the high temperature","the superheat degree will raise"]
一个训练有素的人员独立完成一定工作所需的时间，称作（）。 ["工作设计","工作标准","工作研究","工作方法"]
保护装置的动作评为“正确”和“不正确”的原则是什么？
One of the main purposes of refractories in a boiler furnace is to（） ["help preheat the air for the furnaces","help preheat the feedwater","protect economizer from excessive heat","prevent excessive furnace heat losse"]
补画视图E-27中所缺的图线。
