题干

中东地区是欧亚非三洲的交通要冲,战略地位十分重要。中东战争及巴以冲突,不仅严重影响了该地区的经济和社会发展进程,而且对地区和世界和平构成了严重威胁。导致中东地区局势复杂的主要原因是  (    )

①大国在中东地区的利益争夺

②印度与巴基斯坦的领土争端

③宗教矛盾

④民族矛盾

A:①②③

B:②③④

C:①②④

D:①③④

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答案(点此获取答案解析)

D

同类题3

Values join us together and set us apart. Today, our society has a terrible lack(缺乏)of values. Here are some social values that everyone needs.
◆Respect
Respect means to respect(尊重)others in everyday life. Even if you are against a person, it is important to have respect. It is this respect that makes us human. Without this respect, we become  animals. We need to respect our friends for our friendships. We even need to respect our enemies, because they help us to grow up and be stronger. Respect is one of the crucial values in a relationship.
◆Love
Love is everything. With love in our hearts, we feel no need to hurt another. With love in our hearts, we will pay more attention to the similarities in opinions rather than the disagreement. If we want others to be good to us, we need to be good to them. After all, we give love to get love, right?
◆Loyalty
People often forget the meaning and importance of loyalty(忠诚). Loyalty is necessary for people to believe in each other. In no matter what kind of relationship, we need to believe in each other so that we can work together towards the same goal.
◆Honesty
Honesty is to show other people who we really are. Honesty helps us do better, because it makes us realize our problems and find ways to solve them. It is this honesty, that will make others help you out, not because you need it. But, because they have problems too, which you can help out with. This honesty will help us follow the other values in society and, truly, "heal the world"!

同类题4

阅读《光的全反射》,回答:

光的全反射

    如图1所示,当光线从玻璃斜射入空气里的时候,一部分光会进入空气里发生折射,此时折射角β大于入射角α.若入射角增大时,折射角也随之增大,当入射角增大到某值时(小于90°),折射角会增大到90°.若继续增大入射角,此时空气中没有折射光射出,光线全部反射回玻璃,这种现象叫做光的全反射.折射角等于90°时的入射角称为临界角.当光从水或玻璃射入空气时,只要入射角大于临界角,光就会发生全反射.

海面上出现的海市蜃楼奇景如图2所示,就是因为光的在空气层中多次折射和全反射而形成的自然景观.在夏季,白昼海水温度比较低,所以在海面上方的空气出现下冷上暖的现象.由于空气的热胀冷缩,因此空气层下密上疏.景物的光线先由密的空气层逐渐折射进入稀的空气层,并在上层发生了全反射,光线又折回到下层密的气层中来,经过这样弯曲的线路,最后投入人的眼中.由于人的视觉总是感到物像是来自直线方向的,因此看到的“景物”比实物抬高了许多.

人们利用光的全反射的现象制成了光缆,用于通信等方面.光在均匀透明的玻璃棒中传播,即可在弯曲的玻璃棒的光滑内壁上,借助于接连不断地全反射,可以将光从一端传导到另一端,即使棒的截面直径很小,甚至到微米数量级,传导的效果也不变,这种导光的细玻璃丝称为光导纤维如图3所示.

    光导纤维束已成为一种新的光学基本元件,在光通信、光学窥视及光学特殊照明等方面有重要的应用.荣获2009年诺贝尔物理学奖的华裔科学家高锟在此方面贡献突出,被世界誉为“光纤通讯之父”.

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