为了防止蒸汽被抽走以减轻抽气器的工作负荷,凝结器设置了空气冷却区,其面积约占凝结器总面积的8%~10%()
参考答案:对
. In our class, when the bell rang and the teacher closed his book, it was a ______for everyone to stand up.
A.mark
B.chance
C.signal
D.measure
压力容器内的压力来源分为:压力来自压力容器的外部和压力容器的内部。