文化的演变过程是怎样的？
参考答案：
观念变则态度变，态度变则行为变，行为变则习惯变，习惯变则文化变。
－Is Mr Li in his office?
－No, he _____ in the office. He's ill in hospital. [ ]
A. mustn't be
B. can't be
C. should be
D. needn't be
冠状动脉扩张和动脉瘤最常见的病因是（）
A.冠状动脉夹层
B.红斑狼疮
C.外伤
D.动脉粥样硬化
E.硬皮病
