男性，58岁。胆囊炎胆石症手术后3天，高热持续不退，咳嗽黄脓痰，伴右侧胸痛。胸部X线摄片示右下肺大片实变伴不规则透亮区。

从预防观点来看，为防止手术后医院内获得性肺炎，推荐的措施是（）

A.空气净化

B.进入层流室严格隔离

C.预防性应用广谱抗生素

D.选择性消化道脱污染和保持胃液酸度

E.预防性应用抗真菌药物

She thought I was praising her son, _____ as a matter of fact, I was scolding him for his bad behavior at school.

A．while

B．therefore

C．which

D．so that