慢性阻塞性肺疾病合并慢性肺心病，最常见的死亡原因是
A．心律失常
B．休克
C．消化道出血
D．呼吸衰竭
E．电解质紊乱
参考答案：D
Upon graduation he asked to be sent to _______________.
A．where he is most needed
B．where he needed
C．where he is mostly needed
D．where is he mostly needed
离心风机在运转中常出现的故障及原因是什么？
