题干

为了转播火箭发射的实况,在发射场建立了发射台用于发射广播和电视信号.已知传输无线电广播信号所用电磁波的波段为中波,而传输电视信号所用电磁波的波段为微波,为了不让山地阻挡信号的传播,使城市居民能收听和收看实况,必须通过建立山顶转发站转发无线电广播信号还是电视信号?简述理由.
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答案(点此获取答案解析)

答:电视信号.因为电视信号所用的电磁波的波段为微波,只能沿直线传播,此处受山地阻挡,因此必须在山顶建立转发站,把微波传出去.

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根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

Evaluating (评价)Sources of health Information

Makinggood choices about your own health requires reasonable evaluation. A key firststep in bettering your evaluation ability is to look carefully at your sourcesof healthy information. Reasonable evaluation includes knowing where and how tofins relevant information, how to separate fact from opinions, how to recognizepoor reasoning, and how to analyze information and the reliability of sources.____ 

Goto the original source. Media reports often simplify the results of medicalresearch. Find out for yourself what a study really reported, and determinewhether it was based on good science. Think about the type of study.____

Watchfor misleading language. Some studies will find that a behavior “contributesto” or is “associated with” an outcome; this does not mean that a certaincourse must lead to a certain result.____ Carefully read or listen toinformation in order to fully understand it.

Useyour common sense. If a report seems too good to be true, probably it is. Beespecially careful of information contained in advertisements.____ Evaluate “scientific” statements carefully,and be aware of quackery(江湖骗术).____ Friends and family members can be a greatsource of ideas and inspiration, but each of us needs to find a healthylifestyle that works for us.

Developingthe ability to evaluate reasonably and independently about the health problemswill serve you well throughout your life.

A.The goal of an ad is to sell yousomething.

B.Make choices that are right for you.

C.And examine the findings of theoriginal research.

D.Be sure to work through the criticalquestions.

E.Distinguish between research reportsand public health advice.

F.The following suggestions can help yousort through the health information you receive from common sources.

G.Be aware that information may also beincorrectly explained by an author's point of view.