Ⅱ型呼吸衰竭时，最合适的吸氧浓度为（）
A.<35%
B.35%～40%
C.45%～50%
D.55%～60%
E.>60%
参考答案：A
—What about the football match last night?
—________. I might as well have stayed at home and had a good rest. [ ]
A. It couldn't have been any better
B. It couldn't have been any worse
C. It was the best one
D. There was no better one
某化学反应可以用X+Y→M+R表示．下列关于此反应的说法中，正确的是（ ）
A．若X是单质，则该反应一定是置换反应
B．若Y为金属，则该反应一定生成氢气
C．若X为紫红色金属，则该反应在常温下进行时一定生成蓝色溶液
D．若X和Y的质量之和为10g，则生成M和R的质量之和一定是10g
