题干

边际产量递减规律,指在短期生产过程中,在其他条件(如技术水平)不变的前提下,增加某种生产要素的投入,当该生产要素投入数量增加到一定程度后,再增加该要素所带来的边际产量是递减的(如下图)。假设可变要素投入量为Q,从图中可以推论出(    )

①Q>B时,应增加可变要素投入量

②A<Q<B时,由于可变要素投入量过大,导致产量逐渐减少

③Q=B时,边际产量为0,应优化投入要素的配置

④Q<A时,由于可变要素投入量不足,导致边际产量没有实现最大化

A:①②

B:②③

C:②④

D:③④

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D

同类题2

   Height is just one of the thousands of features your genes decide. In fact, because you have two parents, your genes provide you a height that usually lands somewhere between the height of each parent. If both your parents are tall, then most probably you will be tall, too, but if you have questions about how tall you're going to be, ask your doctor if he or she can help you find it out.
    But genes don't decide everything. For example, eating an unhealthy diet can keep you from growing to your full potential(潜力). Getting plenty of sleep and enough exercise will help you grow to the expected height.
    No doubt you're wondering how fast you should grow. It depends. There's no perfect or right answer. Generally speaking, kids grow about 2 inches (6 centimeters) a year between age 3 and the time when they start puberty (when your body starts changing and becoming more grown up).
    Your doctor will know how your growth has been going over the years. Two centimeters here and 2 inches there are not nearly as important as the height you're at now, how you've been growing up to this point, and what other changes your body may be going through.
    Don't be scared if you seem to have grown a lot in a very short time. Everyone has a growth spurt(高峰)during puberty. The age for starting puberty is about 10 for girls and about 11 for boys. But it can be earlier or later ----between 7 and 13 for girls and 9 and 15 for boys.
    You'll usually begin to notice that you're growing faster about a year or so after your body starts to show the first changes of puberty.

同类题4

阅读文章,完成下列小题。

    真正热爱阅读的人是不需要理由的,从书本中获得的巨大愉悦,足以让人废寝忘食。一个角落、一本书,就能筑起一个完整而缤纷的世界。这也是阅读有别于其他文娱活动的根本特征,即它是不依赖其他感官的、高度个人化的精神活动。通过阅读,我们最终学会如何与自己相处,并在这种周行不殆的智识训练中使精神日益丰富。在这个意义上,阅读乃是每日必须进行的精神刷新。在一次次的刷新中,勤于阅读的人将逐渐成长为一个有着丰富心灵层次,心智成熟的现代人。

    古人讲“三日不读书,便觉言语无味,面目可憎”。这并不仅仅在讲旁观者的感受,更是在提醒自己,不读书就会让灵性蒙尘。那些带着墨香的书页在你指尖哗哗流淌,或记载着高深玄妙的思想,或传递着历史深处的信息,在你的脑海中排列为奇妙而华美的文字城堡。可见,阅读是一个自我教育、自我升华的过程。

    如果说和他人相处是一项必备的社会能力,那么和自己相处则体现一种可贵的精神定力。阅读可以帮助我们培养这种能力。太多人习惯了众声喧哗,却无法和自己平静地相处片刻。只有阅读才能给人这种能力。我们在阅读中学着和自己对话,正如我们在终极的意义上独自面对人生一样。在某种意义上,阅读是对庸常生活的救赎,让我们得以暂时跳脱出琐碎的眼前之事。

    阅读也是为了和这个世界更好相处。我们提倡阅读,并非为了闭门不出、与世隔绝。阅读不是为了逃避世界,而是为了更好地拥抱世界、热爱他人。从阅读中,我们不仅在与高尚人物的灵魂对话,更能见识到比眼前的世界更深邃、更辽阔的另一个世界。这个世界不仅包括人类已知的历史空间,也包括历代经典作家们营造的精神空间。通过这种思接千载、神游八荒的精神活动,我们将学会谦卑,也将变得柔和、平淡,;学着更深地理解他人与世界,更具包容心和同理心地看待这个世界上的诸种缺陷与不足。

    阅读是一项几乎没有门槛的活动,人人都可领略文字之美;阅读又是一项由浅入深的精神历练,需要持之以恒才能登堂入室、窥其堂奥。这个世界需要书籍的火种来点亮,而一个追求内心丰富的人,也总有赖于阅读带来的精神刷新。