As bananas ripen. the green skin turns ye11ow gradually. Chemical changes occur in the f1esh of the fruit as well:starchchanges to sugar,pectinbreaks down.losing its stiffness, and the f1esh softens. 题目和参考答案——青夏教育精英家教网—

题目内容

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.

【答案】

72．A 73．D 74．B 75．B

【解析】略

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相关题目

Emotions Affect Our Bodies

Sometimes people call each other“scaredy-cat”, but have you ever thought about this expression?When a cat is frightened, its heart starts beating faster, its muscles get tense, and there are changes in the chemicals in its blood stream.

Although the cat doesn’t realize this, its body is getting ready for action.

If the danger continues, this animal will do one of the two things. It will defend itself or it will run away as fast as it can.

Something like this also happens to people. When we are excited, angry, scared, or aroused by other emotions, our bodies go through many physical changes. Our hearts beat faster, and our muscles get tense. All of these changes make us more alert and ready to react. We, too, get ready to defend ourselves or run.

Human beings, however, have a problem that animals never face. If we give way to our feelings and let them take over, we can get into trouble. Have you ever said something in anger—or hit somebody—and regretted it later? Have you ever shouted at a teacher, told somebody you were lonely or said you were in love, and then wished later you had kept your mouth shut? It isn’t always wise to express your feelings freely.

Does this mean that it’s smarter always to hide our feelings? No! If you keep feelings of anger, sadness and bitterness hidden away or bottled up inside, your body stays tense. Physical illness can develop, and you can feel churned up inside. It can actually be bad for your health.

Feelings that you keep all bottled up inside don’t just go away. It’s as if you bought some bananas and stuck them in a cupboard. You might not be able to see them, but before long you’d smell them. And if you opened the cupboard, chances are that you’d see little fruit flies hovering all over them. They’d be rotten.

You can try to treat emotions as if they were bananas in the cupboard. You can hide them and you can pretend they don’t exist, but they’ll still be around. And at last you will have to deal with them, just like those bananas.

72. It’s mentioned in the passage that human beings get into trouble because ______.

A. they are not as alert as animals

B. they sometimes can’t control their feelings

C. they always do something wrong to other people

D. they don’t pay any attention to their physical changes

73. The underlined phrase“churned up”in the sixth paragraph means _______.

A. very disappointed B. beaten heavily

C. very frightened D. disturbed badly

74. The author wants to tell us in the last two paragraphs that _______ .

A. you’ll not completely get away from your feelings

B. you should treat emotions as bananas in a cupboard

C. feelings will gradually disappear when you hold them in

D. it is good for your health to keep pleasant feelings inside

75. The author writes this article in order to _______ .

A. tell us that it isn’t good to keep feelings inside

B. give us some advice on how to express our feelings

C. make us deal with feelings in a wise way

D. make us know that it isn’t always wise to express our feelings freely

    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.

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.

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.

As bananas ripen，the green skin turns ye11ow gradually．Chemical changes occur in the flesh of the fruit as well：starch（淀粉）changes to sugar；pectin（果胶）breaks down，losing its stiffness；and the flesh 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 for 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？

1．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．CO₂ from the very ripe banana. D．The limitation of oxygen supply.

2．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

3．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

4．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.

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