题干

用一只平底锅煎饼,每次能同时放2张饼.如果煎1张饼需要2分钟(假定正、反面各需要1分钟),问煎2007张饼至少需要____分钟.
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2007

同类题3

阅读下文,回答问题

动物的奇特语言

    ①人类的信息交流离不开语言。那么,动物有没有“语言”呢?常言说:“人有人言,兽有兽语。”所谓动物的“语言”,一般是指同一种动物之间为了种群的生存和发展传递信息的动作、气味和声音。

    ②动物的动作是一种常见的“语言”。例如,鹿科动物的小尾巴反面是白色的,当它们遇到危险时,就会把尾巴撅起,露出反面的白色,像摇动着白色的“信号”,在绿色丛林地带非常显眼,可以告诉自己的同类:跟我来,快逃跑。工蜂发现蜜源后,会通过圆形舞和“8”字摆尾舞把蜜源的距离和方向告诉自己的同伴。

    ③气味是一种特殊的“语言”。昆虫体表的腺体能分泌信息激素,这是一类挥发性的有独特气味的化学物质。在昆虫释放的信息激素中,最普遍、最灵敏、最专一的,是吸引异性的“性引诱素”。例如,一种雌蛾在交配产卵前,能分泌只有0.1微克的“性引诱素”,但雄蛾依靠头部的触觉,甚至在1公里外都能收到这种信号,几乎只要一个气味分子作用于雄蛾的触角,就足以引诱雄蛾与雌蛾“约会”。蚁、蜂、蚜虫等受到伤害或惊扰时,会放出一种“警戒素”,以告诉同类赶快逃避或奋起自卫。

    ④高等脊椎动物也有气味“语言”。例如,人们在小狗身上抹上母猪的尿液,母猪凭着这种体味信号,会把小狗当作自己的孩子进行哺乳。雄羚羊求偶时,也要靠嗅觉来识别雌羚羊。

    ⑤当然,动物的声音更是一种重要的“语言”。根据动物学家研究,猪有23种声音信号,狐狸有36种声音信号,而阿拉伯狒狒发出的声音信号竟然不少于40种。在模拟声音能力方面,一种叫库科尼亚的鹦鹉会“说”上百个单词和几十句话。

同类题4

根据短文内容,选择正确答案。

Dear Ken,

      I'm glad to hear from you. You asked me how to do well in English exams. Sometimes your knowledge is enough, but you also need good strategies.

 Here are some advice for you:

      Before you answer the questions, if you feel a little nervous, take a few deep breaths to help you relax.

      Always read the question carefully and make sure that you understand it. Read it a few times if possible.

      Find out how much each question is worth or how many points you need.

      If it asks you to give one answer, only give one.

      If there is a difficult question, don't worry. Go on with the next question and come back to it if you have time later.

      Try not to leave questions unanswered when you finish the text. Sometimes a guess may help you get points.

      When you finish, go back and check your answers. You will need to check your writing or spelling mistakes.

     Best wishes to you and your family.

                                                                                                                                                                                Yours,

                                                                                                                                                                                   Amy