急性阑尾炎最常见的原因为（）
A.阑尾血运差
B.异位阑尾
C.阑尾腔内梗阻
D.阑尾系膜过短
E.阑尾壁淋巴组织丰富
参考答案：C
冲裁件的结构工艺性（工艺要求）
Questions 27～30
A. It has a tutorial supervision system. B. It has progressive ideas on education. C. Its professors are more interested in research. D. Its staff maintain a good relation with the students.
