确诊为Ⅱ型呼吸衰竭时纠正缺氧的首选措施是()。
A.面罩给氧
B.鼻导管低浓度给氧
C.鼻导管高浓度给氧
D.无创正压通气
E.机械通气(呼气末正压)
参考答案:B
目前,P2P网络存在______、分布式非结构化、分布式结构化和混合式4种结构类型。
Scarcely _____ raining _____ the PLA fighters started on their way again.
A.it had stopped...before
B.it had stopped...then
C.had it stopped...than
D.had it stopped...when