题干

若x<2,则 x2−4x+4 ____.
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2-x

同类题4

阅读下面短文,掌握其大意,然后从各题所给的四个选项(A、B、C和D)中,选出最佳选项。

    I often read of incidents of misunderstanding or conflict. I'm left1.Why do these people create mistrust and problems, especially with those from other2?

    I was growing up in Kuala Lumpur in the early 1960s,3children from different races and religions played and studied4in harmony. At that time my family lived a stone's5from Ismail's. And no one was bothered that Ismail was a Malay Muslim and I was an Indian Hindu-we just6our differences. Perhaps, our elders had not filled our heads with unnecessary advice, well7or otherwise.

    We were nine when we became friends. During the school holidays, we'd8the countryside on our bicycles, hoping to9the unexpected. At times Ismail would accompany my family as we made a rare shopping trip to town. We would be glad of his10.

    When I was twelve, my family moved to Johor. Ismail's family later returned to their village, and I11touch with him.

    One spring afternoon in 1983, I stopped a taxi in Kuala Lumpur. I12my destination. The driver acknowledged my13but did not move off. Instead, he looked14at me. “Raddar?”he said, using my childhood nickname(绰号). I was astonished at being so15addressed(称呼). Unexpectedly! It was Ismail! Even after two16we still recognized each other. Grasping his shoulder, I felt a true affection, something17to describe.

    If we can allow our children to be18without prejudice, they'll build friendships with people, regardless of race or religion, who will be19their side through thick and thin. On such friendships are societies build and20we can truly be, as William Shakespeare once wrote, “we happy few, we band of brothers”.

同类题5

阅读文段,回答问题。

病毒的话

   我们家族的名称是“病毒”。顾名思义,就是能致病的毒物。因此,人们谈病毒色变。可是,这不能赖我们呀!是你们人类给我们起了这么一个不雅的名称。

   我们也不好怪人类,给我们起这个名称也是有来由的。19世纪末,烟草得了花叶病;荷兰植物学家比林杰克把病的烟叶捣碎,挤出液汁,用没有上釉的瓷过滤器过滤,滤过的液汁用当时最好的显微镜都检查不出有什么细菌,可是它仍然能让烟草得病。比林杰克认为,这一定是比细菌还小的微粒在作怪。他把这类微粒叫做“病毒”,人类就是这样结识了我们。后来发现,人类许多疾病,如流感、麻疹、肝炎等等,其罪魁祸首也都是我们。把我们称作病毒就更有理由了。

   人类的本事越来越大,科学家终于看到了我们的真面目。我们家族最小的成员只有细菌的千分之几那么大,直径只有百万分之一厘米,大的也只有百万分之二十五厘米。(A)我们的构造比细菌还简单的多。我们根本没有细胞结构,只不过是由一个核酸分子(一种记录遗传密码的物质)外包一层蛋白质外壳而已。

   其实同世界万物一样,我们之中有有害的病毒,也有有益的病毒。

    20世纪初,科学家就发现,我们家族中有些成员有孙悟空钻进铁扇公主肚内的本领,能钻进细菌体内,在那里繁殖,使细菌死亡,科学家把它们叫做“噬菌体”。(B)人种了牛痘可以产生对天花的免疫力,牛痘就是经过“改造”后毒性减弱的天花病毒。经过这一番改造,它不仅不再危害人类,还反戈一击,帮助人类消灭这种可怕的传染病。现在许多种疾病的病毒已经被用来制造疫苗为人类服务了。我们家族中还有一些成员叫做“肠道腐生病毒”。它们在婴儿出生以后不久就进入婴儿肠道,在人一生中始终呆在那里。其中有些是有益的。它们可以促进人体产生有防治疾病作用的干扰素,抑制能致病的肠道病毒、流感病毒等等。科学家现在已经制成活肠道病毒、流感病毒等等。科学家现在已经制成活肠道病毒疫苗,它能预防多种传染病,甚至还有一定的抗癌作用哩!