Below is a selection from a popular scie

问题阅读理解

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 a 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 comparison.
Which works harder, your 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（超级油轮）. 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 out when they become damaged, decayed（腐烂）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（收缩）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 simply lose height as their spine (脊柱) becomes 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 an 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, become more bent and curved.
Why does spinning make you dizzy)?
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’re moving while you’re not.
Where do feelings and emotions come from?
Mostly from an ancient part of the brain called the limbic system（边缘系统）. 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 complex 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．Blue	B．Light yellow
C．Red	D．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 becomes 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 complex as those of humans.

D．Our feelings and emotions come 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.

答案

小题1:D

小题2:D

小题3:A

小题4:B

题目分析：你知道我们身体的一些秘密吗？比如血液是红色的，但为什么静脉看起来却是绿色的？等等问题，读完本篇你就会找到答案。

小题1:D考查细节理解。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:D考查细节理解。从第九段的when they do get shorter, it’s not because the spine has shortened a little. Or more often, become more bent and curved.可知老年人变矮不是因为他们的脊柱变短，更多的原因是因为他们的脊柱变弯曲。所以D选项正确。A选项的内容文中没有提及；B选项不符合文中的内容They simply lose height as their spine（脊柱）becomes shorter and more curved due to disuse and the effects of gravity（重力）；C选项的内容与文中的描述相反。

小题3:A考查细节理解。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 complex emotions than any other animal on this planet.可知Ｃ，Ｄ两项错误。

小题4:B考查推理判断。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。