当进料带水严重汽化时,原料油缓冲罐压力分程控制状态是()。
A、A、B两阀均关闭
B、A、B两阀均全开
C、A阀打开,B阀关闭
D、A阀关闭,B阀打开
参考答案:D
土地是重要的生产资料,尤其是在生产力还不发达的古代社会,统治者更是十分重视土地问题的解决。商鞅变法、北魏孝文帝改革、俄国农奴制改革是如何解决土地问题的?这一问题的解决分别产生了什么影响?
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限位开关在电路中的作用是()
A.短路保护
B.过载保护
C.久压保护
D.行程控制