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.

    As bananas ripen， the green skin turns ye11ow gradually. Chemical changes occur in the f1esh of the fruit as well：starch（淀粉）changes to sugar；pectin（果胶）breaks down，losing its stiffness； and the f1esh softens.
Is ripening fruit a self－contained system， or is the rate of these changes affected by the environment？ We designed the experiment below to see if different atmospheres， produced by different packaging， affected the rate of ripening. You will vary the atmosphere surrounding unripe bananas and observe the effect on the ripening process。
Now set up the bananas in their environments as follows：
1. Put two green bananas in a paper bag and fo1d the top over to seal out the air.
2．Put one green banana and the very ripe banana in the other paper bag and fold over the top.
3. Put two green bananas in a plastic bag and seal it.
4. Wrap（包）one green banana tightly in a plastic bag.
5. Leave one green banana exposed to the air.
Leave the fruit a1one or five days to ripen. Ripening fruit“breathes”． This means that it takes up oxygen and gives off C02. Oxygen is extremely important and necessary for the chemical reactions involved in ripening. In addition, ripening fruit gives off another gas, called ethylene（乙烯）. Not only is ethylene a product of ripening fruit, it also promotes the further ripening of the fruit.
Paper bags tend to keep the ethylene in, but they allow oxygen and ethylene to pass through slowly. Plastic bags do not allow the free flow of oxygen or ethylene. In this experiment, the green banana in paper bag with the ripe banana should ripen most quickly. The green bananas in the paper bag should ripen faster than the bananas in the plastic bag. The banana left exposed to air has an unlimited supply of oxygen, so it will turn brown most quickly. You will notice that the side of this banana that rests on the counter will ripen more quickly than the other sides, because it has the
closest contact（接触）with its own ethylene. The banana that is tightly wrapped in plastic has no oxygen supply and should ripen most slowly. Now can you see why bananas are sealed in plastic in many supermarkets？
72. What makes the green banana in Bag 2 ripen more quickly than the ones in Bag 1？
A. Ethylene from the very ripe banana.            B. The free flow of oxygen or ethylene
C. C02 from the very ripe banana.                     D. The limitation of oxygen supply.
73. How can we slow down the ripening of bananas exposed to the air？
A. To rest them on the counter.                                   B. To keep them in the basket.
C. To put them on the ground.                                     D. To hang them up from the ceiling
74. It can be concluded from the passage that          .
A. the ripening banana is a self-contained system
B. the rate of ripening bananas is affected by the environment
C. wrapped bananas experience no chemical changes to ripen
D. ripening bananas give off oxygen, C0, and ethylene
75. Why are bananas sealed in plastic in many supermarkets？
A. To make them ripen more quickly.                B. To make them ripen more slowly.
C. To make banana flesh soften.                        D. To turn green bananas yellow.

Electric cars will not be really much cleaner than autos powered by mineral fuels until they rely less on electricity produced from usual coal-fired power plants.

 “For electric vehicles to become a major green alternative, the power fuel has to move away from

coal, or cleaner coal technologies have to be developed,” said Jared Cohon, the chairman of a National

Research Council report released on Monday. About half of US power is produced by

burning coal, which gives off many times more of traditional pollutants than natural gas, and about

twice as much of the main greenhouse gas carbon dioxide. Nuclear and renewable power have to

generate a larger portion of US power for electric cars to become much greener compared to

gasoline-powered cars, Cohan, who is president of Carnegie Mellon University, said in an interview.

Advances in coal burning, like capturing carbon at power plants for permanent burial underground,

could also help electric cars become a cleaner alternative to vehicles powered by fossil fuels, he said.

Pollution from energy sources did $120 billion worth of damage to human health, agriculture and

recreation in 2008, and electricity was responsible for more than half of the damage, said the NRC

report.

  Electric cars have their benefits such as reducing imports of foreign oil. But they also have hidden

costs. Materials in electric car batteries are hard to produce, which adds to the energy it takes to make

them. In fact, the health and environmental costs of making electric cars can be 20 percent greater

than usual cars, the report said.

  The report estimated that electric cars could still cost more than gas-powered cars to operate and

manufacture in 2030 unless US power production becomes cleaner.[来源:]

1. Why are electric cars not clean enough?

   A. Because they run too slowly              B. Because they are too expensive

   C. Because they rely on coal-fired power.      D. Because they give off more carbon dioxide.

2. We can infer from the passage that ______.

   A. electric cars will soon take the place of gas-powered cars

   B. no one holds hope for electric cars at present

   C. electric cars waste more energy than before

   D. some people believe that electric cars are cleaner

3. The underlined word “them” refers to “______”.

   A. electric cars     B. batteries       C. producers        D. materials

4. Which of the following is NOT mentioned as a way to make electric cars cleaner?

   A. Developing cleaner coal technologies.        B. Making electric cars run faster.

   C. Generating more unclear power.             D. Making advances in coal burning.

 Before a new type airplane goes service, every part of it is tested again and again. But there are two tests that are more of into important than the others.

   The first is called the “tank test”. A modern airplane must fly very high in the sky. Air must be pumped into the plane so that the passengers can breathe. The metal structure of the plane has to be very strong for this reason. When the plane is filled with air, the air presses against the skin of the plane inside. The pressure(压力)on a small window is like a huge foot that is trying to get out. If a small part of the plane were to fail, the plane would explode in the sky. To test the structure of the plane, the plane is lowered into a huge tank or container of water. Then it is filled with air. The pressure inside the plane is greater than it ever will be when it is high up in the air. Finally, there is an explosion. This does not cause so much damage inside the water tank as it would anywhere else. Engineers can discover which part of the plane has broken. Then that part is made stronger.

   The most dangerous test happens when the new plane is going through test flights in the air. The test must find out exactly what happens when the engines(发动机) are all shut off at once. The plane begins to fall like a stone. It is the pilot’s job to find out how he can get control of the plane again. These two tests are examples of how planes are made safe before they ever carry passengers.

By doing the “tank test”, the engineers can find out ____.

   A. the amount of air in the plane                B. the strength of the plane structure

   C. the pressure inside and outside the plane       D. the power of the airplane engines

What will happen to the plane under the “tank test”?

   A. It will be broken                        B. It will be made stronger.

   C. It will be filled with water.                D. It will be tested by pilots.

According to the text, why are test flights most dangerous?

   A. The plane may explode in the air          B. The pilot may lose control of the plane.

   C. The engines may be damaged.             D. Too much air may get into the plane.

What might be the most suitable title for the text?

  A. Two Important Tests on Airplane           B. The Importance of Flying Safety

  C. The Danger of Testing Airplanes            D. How Airplanes Are made and Tested

C

While they were almost unknown twenty years ago, it seems that mobile phones these days are part of everyone’s life. However, as with other inventions such as the television and the computer, they are a double-edged sword, inviting both supporters and opponents, especially in regard to their use in public places like restaurants and cinemas.

One of the strongest arguments in favor of forbidding mobiles in public places is the trouble they cause to other people. For example, although we are often asked to turn off our phones when in a cinema, the film that we are watching is often interrupted by the sound of at least five rings. To make it even worse, some people insist on continuing their conversation, even though hundreds of people can hear what they say, which often drowns out the voice from the film. As a result, many people would welcome a ban on mobile phones in places where they might disturb other people.

On the other hand, there are a number of arguments against such a ban. It is difficult to stop people bringing with them their mobile phones in public places, making it almost impossible to call for a ban. Some people would see this as an infringement（侵犯）of their rights, while other people would say they need them in case of an emergency. Despite being asked to silence their phones, some people insist on leaving them on.

It seems to me that a ban on mobile phones would not have any result in the end. People will find a way to escape a ban. Nevertheless, people should be discouraged from using them in public places, unless it is highly necessary. They should be made to know that it is bad manners to use them in certain places or at certain times. Of course, there will always be someone who thinks their call is more important than others’ peace and quiet!

53. Why are many people for a ban on the use of mobiles in public places?

A. Because hundreds of people can hear them talk.

B. Because they are asked to turn off their mobiles.

C. Because other people’s peace and quiet is more important.

D. Because many people find a way to escape a ban.

54. Among those who are against a ban, some believe that __________.

A. they can turn off their mobiles when it is necessary

B. it is their right to use their mobiles in public places

C. a ban on mobiles would not have any result

D. they can silence their mobiles when in public places

55. The author of the text thinks that __________.

A. mobiles can be used in case of an emergency in public places

B. mobiles should be turned off in public places

C. mobiles should not be banned in public places

D. it is possible to ban the use of mobiles in public places

56. Which of the following would be the best title for the text?

A. Disadvantages of Mobiles in Public Places

B. Why Not Ban Mobiles in Public Places?

C. Should Mobiles Be Banned in Public Places?

D. Manners for Mobile Users in Public Places