题干

下列说法正确的是(   )

A:新型电热毯的电阻丝是用超导体材料制成的

B:LED灯中的发光二极管主要是由半导体材料制成的

C:人们利用超声波的反射制成的声呐来测量地球到月球的距离

D:太阳内部每时每刻都在发生裂变释放巨大的核能

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答案(点此获取答案解析)

B

同类题1

阅读下面的文字,完成各题。

手机是条“贪吃蛇”

       ①过去的10多年里,随着技术进步,手机已经越来越神通广大。它就像当年那款游戏中的“贪吃蛇”,在通话的“本能”之外,已经吃掉了演播上游戏机、卡片式相机,MP3音乐播放器、电子词典和录音笔等设备,现在,它又咬住了电子导航、移动支付等猎物,彻底改变了一些产业的形态,让卡西欧等老牌公司损失惨重。

       ②个人用品也成了这只贪吃蛇进攻的目标,手环、手表、眼镜一类可佩戴设备,大有被它吞噬的趋势;就连牙刷这样的生活必需品,也被它叼进了嘴。最近,已经有生产商推出了一款电动牙刷,可以根据使用者刷牙时对手柄的压力,采集口腔中每颗牙齿的信息,在手机上生成牙齿情况的全息图,并定期生成牙齿情况报告,提出健康建议,甚至帮助使用者与牙医进行信息交流。

       ③手机已经进化成为社交生活的路由器,人们日惯了通过电话或微信联糸,甚至离开它就无法正常沟通,手机依赖症和交流恐惧症开始在人类社会蔓延。

       ④手机,看上去已经无所不能。当客厅里的电视、书房里的电脑、卧室里的睡眠记录仪、盥洗室里的牙刷,乃至车库里的车辆都被手机一一攻克后,谁会是电子设备们最后的堡垒?

(选自《财经国家周刊》2014年第7期,有删改)

同类题2

完形填空。阅读下面的短文,掌握其大意,然后从各题所给的四个选项中选出一个最佳答案。

    Once again, I was at a new school.1was a girl in my class named Paris. That was where the similarities ended.

    I was tall and she was small. I was one of the 2 in the class while she was the youngest. My hair was thick, short and ugly while hers was long and beautiful. I couldn't stand her, considering her my 3. But she wanted to be friends.

    One day, she invited me over and I said yes – I was too 4 to say no. Actually, no one had invited me over to 5 before. But this girl, who wore the latest fashions, wanted to see me.

    When we got to the 6 she shared with her sister, she took out a big case of Barbies – which was my next surprise. I had never played with them. But we sat on the floor of a walk-in cupboard 7 as we made up crazy stories about the Barbies. That's when we 8 that we both wanted to be writers when we were older. We both had wild 9.

    We had a great time that afternoon. Our jaws (下巴) ached from smiling so much. She 10 me her outfits, which had mostly come from a designer clothing store. The woman who owned it sometimes used her 11a model for her newspaper ads and gave her clothes in exchange.

    Paris charmed the whole neighborhood. The 12owners lent her fashion magazines down the block, the movie theater gave her free passes and the pizza place let her 13free pieces. Soon I was included in her 14 world. We slept over at each other's houses and spent every free moment together.

    Paris, my first real friend since childhood, helped me get through my tough teenage 15and taught me an amazing thing about making friends: Your “worst enemy” can turn out to be your best friend.