心肌梗死的最基本病因是
A．冠状动脉栓塞
B．冠状动脉炎症
C．冠状动脉粥样硬化
D．冠状动脉先天性畸形
E．冠状动脉痉挛
参考答案：C
Mary ______ a beautiful dress for her little sister last Saturday. [ ]
A. buys
B. bought
C. is buying
D. will buy
以氯丁胶和石油为基料制成的防水涂料，有（）两类。
A.溶剂型
B.固态
C.液态
D.乳液型
