若函数y=a $x^{a^2-2a-6}$是二次函数且图象开口向上，则a=（　　）

鲁迅自传

    我于一八八一年生于浙江省绍兴府城里的一家姓周的家里。父亲是读书的；母亲姓鲁，乡下人，她以自修得到能够看书的学力。听人说，在我幼小时候，家里还有四五十亩水田，并不很愁生计。但到我十三岁时，我家忽而遭了一场很大的变故，几乎什么也没有了；我寄住在一个亲戚家里，有时还被称为乞食者。我于是决心回家，而我底父亲又生了重病，约有三年多，死去了。我渐至于连极少的学费也无法可想；我底母亲便给我筹办了一点旅费，教我去寻无需学费的学校去，因为我总不肯学做幕友或商人，——这是我乡衰落了的读书人家子弟所常走的两条路。

    其时我是十八岁，便旅行到南京，考入水师学堂了，分在机关科。大约过了半年，我又走出，改进矿路学堂去学开矿。毕业之后，即被派往日本去留学。但待到在东京的预备学校毕业，我已经决意要学医了。原因之一是因为我确知道了新的医学对于日本维新有很大的助力。我于是进了仙台（Sen－dai）医学专门学校，学了两年。这时正值俄日战争，我偶然在电影上看见一个中国人因做侦探而将被斩，因此又觉得在中国医好几个人也无用，还应该有较为广大的运动……先提倡新文艺。我便弃了学籍，再到东京，和几个朋友立了些小计划，但都陆续失败了。我又想往德国去，也失败了。终于，因为我底母亲和几个别的人很希望我有经济上的帮助，我便回到中国来；这时我是二十九岁。

    我一回国，就在浙江杭州的两级师范学堂做化学和生理学教员，第二年就走出，到绍兴中学堂去做教务长，第三年又走出。没有地方可去，想在一个书店去做编译员，到底被拒绝了。但革命也就发生，绍兴光复后，我做了师范学校的校长。革命政府在南京成立，教育部长招我去做部员，移入北京；后来又兼做北京大学、师范大学、女子师范大学的国文系讲师。到一九二六年，有几个学者到段祺瑞政府去告密，说我不好，要捕拿我，我便因了朋友林语堂的帮助逃到厦门，去做厦门大学教授，十二月走出，到广东做了中山大学教授，四月辞职，九月出广东，一直住在上海。

    我在留学时候，只在杂志上登过几篇不好的文章。初做小说是一九一八年，因为一个朋友钱玄同的劝告，做来登在《新青年》上的。这时才用“鲁迅”的笔名（Pen－name）；也常用别的名字做一点短论。现在汇印成书的有两本短篇小说集：《呐喊》，《彷徨》。一本论文，一本回忆记，一本散文诗，四本短评。别的，除翻译不计外，印成的又有一本《中国小说史略》，和一本编定的《唐宋传奇集》。

一九三○年五月十六日

如图，数轴上有A，B，C，D四个点，其中到原点距离相等的两个点是（　　）

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    Are you interested in some of the most popular brands such as Beats headphones, True Religion jeans, and UGG shoes? They are also expensive. But some experts say they are not much better than cheaper brands.

    For example, Jim Wilcox works for Consumer Reports. He tested all kinds of headphones. He says that $80 Koss Pro headphones provide basically the same quality and comfort as Beats. So why do people pay twice or even 10 times as much for the hottest brands?

    Experts say it's because fashionable, expensive brands send a message. Brands say “I belong” or “I can afford it.”

    Some people think that expensive brand names are worth the price. They say that some designer clothes are really top quality and that they last longer than cheaper brands. Some teenagers choose to wear popular brands because these brands make them feel good about themselves.

    Alexandra Allam, 17, likes to buy brand-name products. “I'd rather spend the extra money to get something I know I'll be satisfied with,” she says. Her friend Emmy Swan agrees, saying “As long as you can afford it, it seems reasonable to buy what you want.” But not all teenagers agree. “Spending hundreds of dollars for designer sunglasses is stupid and unreasonable,” says Daniel Steinbrecher, 16. “It's fake (假的) happiness.”

    People who are against wearing expensive brand names say that many designer brands aren't any better. “It's wasteful to buy things just because they are popular,” says Edmund Williams, 15. “You'll feel better if you buy things because you like them. If you have extra money to spend, it would be better to give it to people in need.”