正常二尖瓣开口面积为 （）
A.4～6cm2
B.2～4cm2
C.3～4cm2
D.1～2cm2
E.6～8cm2
参考答案：A
单词拼写。
1. Do you have a driver's l ?
2. What he said sounds impossible, so I d with him.
3. He l the stone and threw it.
4. Old women like (闲谈) with others.
5. I'd like to give it to (医学) research.
决定系统静态性能和动态性能的系统的（）。
A.零点和极点
B.零点和传递系数
C.极点和传递系数
D.零点、极点和传递系数
