左心衰竭患者发展为全心衰竭后呼吸困难减轻。
参考答案：对
— ______?
—They are tables.[ ]
A. What are they?
B. What's this
C. What color are you
D. Where are they
循环压缩机的轴封是采用的密封形式是（）密封。
A、机械
B、油膜
C、干气
D、空气
