Question

Below is a selection from a popular science book.

If blood is red, why are veins（靜脈）blue?

Actually, veins are not blue at all. They are more of a clear, yellowish colour. 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 colour. 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. But, in the long run, your brain probably tips it, because even when you’re sitting still your brain is using twice as much 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-up?

Baby (or “milk”) teeth do not last long; they fall out to make room for bigger, stronger adult teeth later on. Adult teeth fall out when they become damaged, decayed and infected by bacteria. Once this second set of teeth has grown in, you’re done. When they’re gone, they’re 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 simply lose height as their spine(脊柱)becomes shorter and more curved due to disuse and the effects 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(眩暈的)?

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 and balance stable. But, when you suddenly stop spinning the system goes out 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. 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 animals on the 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.

1.What is the colour of blood in a vein near the surface of the skin?

A. Blue B. Dark reddish purple

C. Red D. Light yellow

2.Why do some old people look a little shrunken as they age?

A. Because their spine become more bent.

B. Because they are more easily affected by gravity.

C. Because they keep growing backwards.

D. Because their spine is in active use.

3.Which of the following statements about our brain is true?

A. The brains of the other mammals are as complex as those of humans.

B. When our brain senses the spinning, we will feel dizzy.

C. In the long run, our brain probably works harder than our heart.

D. Our feelings and emotions come from the most developed area in our brain.

4.. In this article, we can know except _____.

A. it takes four to five times as much blood to feed our brain as to feed our heart.

B. when adult teeth are gone, they cannot grow back.

C. the reason why spinning make us dizzy.

D. how we can grow taller.

5. What is the main purpose of the selection?

A. To give advice on how to stay healthy.

B. To report the latest discoveries in medical science.

C. To challenge new findings in medical research.

D. To provide information about our body.

 

Answer 1

1.B

2.A

3.C

4.D

5.D

【解析】

試題分析: 文章從科學(xué)的角度解釋了幾個人們普遍感到困惑的問題。比如，為什么血液是紅色的而血管卻呈現(xiàn)出深藍色呢？為什么牙齒會掉而且成年后不再長出新的牙齒呢？為什么人老了身高就變矮了呢？讀了這篇文章以后，你就會恍然大悟。

1.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.可知在靠近皮膚表層的血管里，血液是紫紅色，故B選項正確。

2.細節(jié)理解題。從文章第四段When they do get shorter, it’s because the spine has shortened a little. Or, more often, become more bent and curved.可知A選項正確。

3.推理判斷題。根據(jù)文章第二段, 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.我們可以推斷從長遠看來，大腦要比心臟工作更多。所以C選項正確。

4.細節(jié)理解題。根據(jù)文章第一段對血液的介紹，第三段對牙齒的介紹和第五段的內(nèi)容介紹我們可以了解到ABC三項內(nèi)容，但是D選項內(nèi)容是文章沒有涉及到的，故答案選D。

5.推理判斷題。本文節(jié)選自科普圖書，給人們介紹了一些人體的科學(xué)知識，比如血液、牙齒和骨骼等等，由此判斷D選項正確。

考點：考查科學(xué)知識類短文閱讀。