Below is a selection from a popular science book.
If blood is red, why are veins（静脉） blue?
Actually, veins are not blue at all. They are more of a clear, yellowish color. Although blood looks red when it’s outside the body, when it’s sitting in the vein near the surface of the skin, it’s more of a dark reddish purple color. At the right depth, these blood-filled veins reflect less red light than the surrounding skin, making them look blue by parison.
Which works harder, you heart or your brain?
That kind of depends on whether you’re busy thinking or busy exercising. Your heart works up to three times harder during exercise, and shifts enough blood over a lifetime to fill a supertanker. But in the long run, your brain probably tips it, because even when you’re sitting still your brain is using twice as much energy as your heart, and it takes four to five times as much blood to feed it.
Why do teeth fall out, and why don’t they grow back in grown-ups?
Baby (or “milk”) teeth do not last long; they fall out to make bigger room for bigger, stronger adult teeth later on. Adult teeth fall our when they bee damaged, decayed and infected by bacteria. Once this second set of teeth has grown in, you’re done. When they’re gone, they are gone. This is because nature figures you’re set for life, and what controls regrowth of your teeth switches off.
Do old people shrink as they age?
Yes and no. Many people do get shorter as they age. But, when they do, it isn’t because they’re shrinking all over. They lose height as their spine（脊柱） bees shorter and more curved due to disuse and the effect of gravity(重力). Many (but not all) men and women do lose height as they get older. Men lose and average of 3-4 cm in height as they age, while women may lose 5 cm or more. If you live to be 200 years old, would you keep shrinking till you were, like 60 cm tall, like a little boy again? No, because old people don’t really shrink! It is not that they are growing backwards ----- their legs, arms and backbones getting shorter. When they do get shorter, it’s because the spine has shortened a little. Or, more often, bee more bent and curved.
Why does spinning make you dizzy（眩晕的）?
Because your brain gets confused between what you’re seeing and what you’re feeling. The brain senses that you’re spinning using special gravity-and-motion-sensing organs in your inner ear, which work together with your eyes to keep your vision balance stable. But when you suddenly stop spinning the system goes out of control, and your brain thinks you’removing while you’re not.
Where do feelings and emotions e from?
Mostly from an ancient part of the brain called the limbic system. All mammals have this brain area ----- from mice to dogs, cats, and humans. So all mammals feel basic emotions like fear, pain and pleasure. But since human feelings also involve other, newer bits of the brain, we feel more plex emotions than any other animal on this planet.
If exercise wears you out, how can it be good for you?
Because our bodies adapt to everything we do to them. And as far as your body is concerned, it’s “use it, or lose it”! It’s not that exercise makes you healthy, it’s more that a lack of exercise leaves your body weak and easily affected by disease
【小题1】What is the color of blood in a vein near the surface of the skin?A．BlueB．Light yellowC．RedD．Dark reddish purple【小题2】Why do some old people look a little shrunken as they age?A．Because their spine is in active use.B．Because they are more easily affected by gravity.C．Because they keep growing backwards.D．Because their spine bees more bent.【小题3】Which of the following statements about our brain is true?A．In the long run, our brain probably works harder than our heart.B．When our brain senses the spinning, we will feel dizzy.C．The brains of the other mammals are as plex as those of humans.D．Our feelings and emotions e from the most developed area in our brain.【小题4】What is the main purpose of the selection?A．To give advice on how to stay healthy.B．To provide information about our body.C．To challenge new findings in medical research.D．To report the latest discoveries in medical science.D
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(答案→)D
解析：
【小题1】根据第一段第二句Although blood looks red when it’s outside the body, when it’s sitting in the vein near the surface of the skin, it’s more of a dark reddish purple color.很容易判断出选Ｄ。
【小题2】根据第四段最后一句Or, more often, bee more bent and curved.可以判断选Ｄ。
【小题3】根据第二段最后一句But in the long run, your brain probably tips it, because even when you’re sitting still your brain is using twice as much energy as your heart, and it takes four to five times as much blood to feed it.可知Ａ项正确。通过第五段最后一句But when you suddenly stop spinning the system goes out of control, and your brain thinks you’removing while you’re not可知当我们突然停止旋转时才会感到眩晕，所以Ｂ项错误；通过第六段最后一句But since human feelings also involve other, newer bits of the brain, we feel more plex emotions than any other animal on this planet.可知Ｃ，Ｄ两项错误。
【小题4】本篇的写作意图就是让我们了解我们的身体，为我们提供一些基本的信息，故Ｂ项正确。