我国公安机关的宗旨是______。
A.维护国家安全B.维护社会治安C.保卫人民民主专政的 * * D.全心全意为人民服务
参考答案:D
Tony ________ for the company as an engineer for two decades. Now he teaches mechanics in Peking University.
A.has worked
B.worked
C.is working
D.had worked
急性前间壁心梗时,冠状动脉病变常见的部位是()
A.左冠状动脉主干
B.左冠状动脉前降支
C.左冠状动脉回旋支
D.左冠状动脉
E.以上都不是