应用血流的流率守恒定律可计算（）
A.瓣口体积
B.瓣口内径
C.瓣口面积
D.瓣口流速
E.瓣口流速时间积分
参考答案：C
Unix系统采用了 【6】 文件系统，具有良好的安全性、保密性和可维护性。
根据汉语提示补充短文。
I have 1. (三位新老师). My English teacher is Mr. Wu. He is 2. (又瘦又高). He is
3. (很滑稽). My P.E. teacher is very 4. (壮). He is 5. (很亲切). My art teacher is a
lady. She is 6. (很年轻). She is 7. (来自加拿大). She is 8. (很文静). She is 9.
(很严格). I 10. (喜欢) them. They like me, too.
