主动脉瓣中度狭窄时瓣口面积为（）
A.<0.75cm2
B.0.75～1.0cm2
C.1.1～1.75cm2
D.1.76～2.0cm2
参考答案：B
Please read every sentence . The more ______ you are, the fewer mistakes you'll make. [ ]
A. carefully; carefully
B. careful; careful.
C. carefully; careful
顶循泵抽空时，应（）。
A、适当提高塔顶温度
B、适当降低中段温度
C、先打冷回流，后切换备用泵
D、及时切换备用泵
