肺泡液-气界面的表面张力属于
A．黏滞阻力
B．惯性阻力
C．气道阻力
D．肺弹性阻力
参考答案：D
I would have attended your birthday party last night but for the fact that it at that time．
A．was raining
B．would rain
C．had rained
D．had been raining
活塞顶部的形状有（）
A、平顶
B、凹顶
C、凸顶
D、凹坑
