在哪个解决问题的方法中需要深刻理解OSI模型。（）
A.实例对照法
B.分步法
C.试错法
D.替换法
参考答案：B
By the end of last week 611 people from 49 countries _______ to attend the meeting, with
nearly half from the United States, Germany and Britain. [ ]
A. had registered
B. have registered
C. registered
D. were registered
诊断Ⅱ型呼吸衰竭的血气标准是（）
A.HC03->32mmol／L
B.pH<7.35
C.PsO<60mmHg，PaCO>50mmHg
D.血氧饱和度<80％
E.动脉氧分压<60mmHg
