呼吸性酸中毒合并代谢性碱中毒的血气改变有（）
A.pH下降
B.HCO3-减少
C.血钾降低
D.血氯降低
E.二氧化碳分压下降
参考答案：C, D
风湿病常见的联合瓣膜损害是
A．二尖瓣和肺动脉瓣B．二尖瓣和三尖瓣C．二尖瓣和主动脉瓣D．主动脉瓣和肺动脉瓣
He is over fifty, but he looks as though he（）only in his thirties.
A.were
B.is
C.will be
D.has been
