压力控制通气和压力支持通气的基本不同点是（）。

A.压力时间波形图的外观

B.吸气如何结束

C.限制患者吸气压力高值的能力

D.初始呼吸机的流速

E.吸气如何开始

As the prisoner had been ______from the outside world for twenty years, he had no idea what the

outside world was like.      [      ]

A. cut off    

B. cut away    

C. cut out    

D. cut short