诊断试验检出阳性患病者的百分率的指标是()A．检测灵敏度 B．临床敏感度 C．检测准

一位社会学家对两组青少年做了研究。第一组成员每周看有暴力内容的影视的时间平均不少于10h；第二组则不多于2h。结果发现第一组成员中举止粗鲁者所占的比例要远高于第二组。因此，此项研究认为，多看有暴力内容的影视容易导致青少年举止粗鲁。 以下哪项如果为真，将对上述研究的结论提出质疑

A．第一组中有的成员的行为并不粗鲁。

B．第二组中有的成员的行为比第一组有的成员粗鲁。

C．第一组中有的成员的文明行为是父母从小教育的结果，这使得他们能抵制暴力影视的不良影响。

D．第一组成员中很多成员的粗鲁举止是从小养成的，这使得他们特别爱看暴力影视。

E．第二组中很多成员的行为很文明。

采用小型机具进行混凝土振捣施工时，振捣棒至模板边缘的距离不宜大于( )mm。

A．100

B．200

C．300

D．500

A good modern newspaper is an extraordinary piece of reading. It is remarkable first for what it contains the range of news from local crime to international politics, from sports to business to fashion to science, and the range of comment and special features (特定) as well, from editorial page to feature articles and interviews to criticism of books, art, theatre and music. A newspaper is even more remarkable for the way one reads it never completely, never straight through, but always by jumping from here to there, in and out glancing at one piece, reading another article all the way through, reading just a few paragraphs of the next.

A good modern newspaper offers a variety to attract many different readers, but far more than any one reader is interested in. What brings this variety together in one place is its topicality (时事性), its immediate relation to what is happening in your world and your locality now. But immediacy and the speed of production that goes with it mean also that much of what appears in a newspaper has no more than transient (短暂的) value.

For all these reasons, no two people really read the same paper: what each person does is to put together out of the pages of that day’s paper, his own selection and sequence, his own news paper. For all these reasons, reading newspapers efficiently, which means getting what you want from them without missing things you need but without wasting time, demands skill and self-awareness as you modify and apply the techniques of reading.

It can be conclude from the passage that newspaper readers ().

A. apply reading techniques skillfully

B. jump from one newspaper to another

C. appreciate the variety of a newspaper

D. usually read a newspaper selectively

若在斜坡上架设仪器，应使三脚架（）。

A、两条腿在坡下，可稍放短些

B、两条腿在坡下，可稍放长些

C、一条腿在坡下，可稍放长些

D、一条腿在坡下，可稍放短些

在经济学研究中采用数学方法的必要性和局限性。