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 comparison.
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 become 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） 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 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, become 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 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 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?

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. 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 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 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 (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’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 （哺乳动物）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 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 color of blood in a vein near the surface of the skin?

A. Blue      B. Light yellow

C. Red        D. Dark reddish purple

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.

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.

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 comparison.

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 become 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） 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 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, become 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 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 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

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

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.

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.

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.

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. 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 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 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 (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’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 （哺乳动物）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 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. 1.

   What is the color of blood in a vein near the surface of the skin?

   1. A.
      Blue
   2. B.
      Light yellow
   3. C.
      Red
   4. D.
      Dark reddish purple
2. 2.

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

   1. A.
      Because their spine is in active use
   2. B.
      Because they are more easily affected by gravity
   3. C.
      Because they keep growing backwards
   4. D.
      Because their spine becomes more bent
3. 3.

   Which of the following statements about our brain is true?

   1. A.
      In the long run, our brain probably works harder than our heart
   2. B.
      When our brain senses the spinning, we will feel dizzy
   3. C.
      The brains of the other mammals are as complex as those of humans
   4. D.
      Our feelings and emotions come from the most developed area in our brain

Uh­oh, the new year's just begun and already you're finding it hard to keep those resolutions to junk the junk food，get off the couch or kick smoking. There's a biological reason why a lot of our bad habits are so hard to break—they get deep­rooted in our brains.

That's not an excuse to give up. Understanding how unhealthy behaviors become deep­rooted has scientists learning some tricks that may help good habits replace the bad.“Why are bad habits stronger? You're fighting against the power of an immediate reward. We all as creatures give greater value to an immediate reward than something that's delayed，” says Dr Nora Volkow, director of the National Institute on Drug Abuse.

Just how that bit of happiness turns into a habit involves a pleasure­sensing chemical named dopamine(多巴胺). It trains the brain to want that reward again and again—increasing the connection each time—especially when it gets the right cue(暗示) from your environment.

People tend to overestimate their ability to resist temptations around them, thus destroying attempts to get rid of bad habits. Even scientists who recognize it find it hard to resist.“I don't like popcorn. But every time I go to the cinema, I have to eat it，” Volkow says.“It's fascinating.”

A movement to pay people for behavior changes may make use of that connection, as some companies offer employees immediate payments for adopting better habits. However paying for behavior turns out, researchers say there are some steps that may help counter your brain's hold on bad habits: repeat，repeat，repeat the new behavior—the same routine at the same time of day. Determined to exercise？Doing it at the same time of the morning makes the brain recognize the habit eventually. If you don't do it, you feel awful. Exercise itself raises dopamine levels, so eventually your brain will get a feel­good hit even if your muscles protest. Reward yourself with something you really desire, Volkow stresses. You exercised all week? Stuck to your diet? Buy a book, a great pair of jeans, or try a fancy restaurant.

20．What's the subjective reason for being hard to break bad behaviors?

A．Some behaviors get deep­rooted in our brains.

B．We prefer an immediate reward.

C．We value delayed gifts.

D．We are all creatures of nature.

21．What does the underlined word “connection” in Paragraph 3 refer to?

A．Pleasure and behavior.  　B．Brain and reward.

C．Happiness and dopamine.  　D．Cue and environment.

22．It can be inferred that the higher the dopamine level is，________．

A．the harder it is for you to break the bad habit

B．the less pleasure you will get

C．the stronger bad habits will become

D．the more you'll want to get a reward

23．Why does Volkow eat popcorn even though he doesn't like it?

A．Because he recognizes the importance of him.

B．Because it is needed for normal growth of the body.

C．Because he can't resist the temptation of it.

D．Because it makes him relaxed to eat popcorn while seeing films.