汽包是锅炉水的加热、（）、（）的一个连接点和分界点。
参考答案：蒸发；汽化
The play had already been on for quite some time when we _______ at the New Theatre.
A．have arrived
B．arrived
C．had arrived
D．arrive
慢性呼吸衰竭的机械通气指征是（）
A.PaO2<45mmHg
B.pH<7.3，PaCO2>80mmHg
C.合并多脏器功能衰竭
D.意识障碍，呼吸不规则
E.呼吸道分泌物多，有排痰障碍
