一项病例对照研究，500名病例中有暴露史者400例，而500名对照中_爱下问搜题

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问题单项选择题

一项病例对照研究，500名病例中有暴露史者400例，而500名对照中有暴露史者100例，其OR值为( )

A．1.25

B．1.6

C．16

D．160

E．无法计算

答案

参考答案：C

解析：OR值指在病例对照研究中，两组之间的患病率之比。表示疾病与暴露因素之间的统计学关系强度。

完形填空

完形填空。
Have you ever complained why life is so tiring? Does the sky sometimes seem dark to you? Are your lessons sometimes not successful? Well, friends, cheer up and __1__ all the time. If you see the world with your warm heart, you'll __2__ the whole world smiling to you. On a sunny morning, you plan to have a walk __3__ yourself. Just before you go out, it suddenly starts to rain. Maybe you would feel very sad and start to complain about the weather. But dear friends, why __4__ sit down and listen to the free concert that the nature brings you? And with the timely rain, crops (庄稼) in the fields will grow better and farmers will have a good harvest (收成). Everyone wants to succeed in what he tries to do, __5__ life isn't a bed of roses. It's very common to meet difficulties on the way __6__ success. In fact, difficulty isn't terrible. The real terrible thing is that we are afraid of it. Difficulty is like spring (弹簧). If you are __7__ , it will be strong. Attitude (态度) decides __8__ . With an optimistic (乐观的) attitude, life is easy and __9__ . So when you meet difficulties, don't give up. Instead, you should face them with a smile. Remember these five rules: Free your heart from hate; Free your mind from worries; Live an easy life; Give more; Expect __10__ .
( ) 1.A. happy ( ) 2.A. look ( ) 3.A. enjoying ( ) 4.A. don't ( ) 5.A. but ( ) 6.A. of ( ) 7.A. energetic ( ) 8.A. anything ( ) 9.A. please ( ) 10. A. little	B. unhappy B. look for B. to relax B. didn't B. and B. to B. powerful B. something B. pleasure B. few	C. smile C. find C. relax C. haven't C. or C. about C. confident C. everything C. pleased C. less	D. cry D. find out D. enjoy D. not D. so D. for D. weak D. nothing D. pleasant D. fewer

单项选择题

摄像机的各项技术指标为最优，图像质量最好（）。

A、广播级

B、专业级

C、家用级

D、业余级