在研究冠心病危险因素病例对照研究中,所选择的对照不能包括()
A.胆结石患者
B.高血压患者
C.消化性溃疡患者
D.白内障患者
E.肺气肿患者
参考答案:B
() when she started complaining.
A.Not until he arrived
B.No sooner had he arrived
C.Hardly had he arrived
D.Scarcely did he arrive
钻开产层以后,将油层套管下至产层顶部,注入水泥完井叫()完井。
A、尾管射孔
B、后期裸眼
C、砾石充填
D、套管射孔