热力管道进行暖管的主要目的是（）。
A、以防送汽时产生水击
B、用蒸汽吹扫管道
C、驱除空气
参考答案：A
_____ he has been away from the city for two years. [ ]
A. It seemed that
B. It seems that
C. He seems that
D. They seem that
在总补体活性测定时，所测定的是( )
A．红细胞与补体结合的能力B．补体溶解红细胞的活性C．补体溶解致敏红细胞的活性D．溶血素与补体结合能力
