We all enjoy the colors of autumn leaves. Did you ever wonder how and why a fall leaf changes color? Where do the yellows and oranges come from? To answer those questions, we first have to understand what leaves are and what they do.
Leaves are nature's food factories. Plants take water from the ground through their roots. They take a gas called carbon dioxide from the air. Plants use sunlight to turn water and carbon dioxide into glucose, which is a kind of sugar. Plants use glucose as food for energy and as a building block for growing. The way plants turn water and carbon dioxide into sugar is called photosynthesis, which means " putting together with light. " A chemical called chlorophyll helps make photosynthesis happen. Chlorophyll is what gives plants their green color.
As summer ends and autumn comes, the days get shorter and shorter. This is how the trees "know" to begin getting ready for winter.
During winter, there is not enough light or water for photosynthesis. The trees will rest, and live off the food they stored during summer. They begin to shut down their food-making factories. The green chlorophyll disappears from the leaves. As the bright green fades away, we begin to see yellow and orange colors. Small a-mounts of these colors have been in the leaves all along. Covered up by the green chlorophyll, we just can't see them in summer.
The bright reds and purples we see in leaves are made mostly in the fall. In some trees, like maples, glucose is trapped in the leaves after photosynthesis stops. Sunlight and the cool nights of autumn cause the leaves turn this glucose into a red color. The brown color of trees like oaks is made from wastes left in the leaves.
It is the combination of all these things that make the beautiful colors we enjoy in the fall.
【小题1】The writer asked two questions in the beginning in order to        .

We all enjoy the colors of autumn leaves. Did you ever wonder how and why a fall leaf changes color? Where do the yellows and oranges come from? To answer those questions, we first have to understand what leaves are and what they do.

      Leaves are nature's food factories. Plants take water from the ground through their roots. They take a gas called carbon dioxide from the air. Plants use sunlight to turn water and carbon dioxide into glucose, which is a kind of sugar. Plants use glucose as food for energy and as a building block for growing. The way plants turn water and carbon dioxide into sugar is called photosynthesis, which means " putting together with light. " A chemical called chlorophyll helps make photosynthesis happen. Chlorophyll is what gives plants their green color.

      As summer ends and autumn comes, the days get shorter and shorter. This is how the trees "know" to begin getting ready for winter.

      During winter, there is not enough light or water for photosynthesis. The trees will rest, and live off the food they stored during summer. They begin to shut down their food-making factories. The green chlorophyll disappears from the leaves. As the bright green fades away, we begin to see yellow and orange colors. Small a-mounts of these colors have been in the leaves all along. Covered up by the green chlorophyll, we just can't see them in summer.

     The bright reds and purples we see in leaves are made mostly in the fall. In some trees, like maples, glucose is trapped in the leaves after photosynthesis stops. Sunlight and the cool nights of autumn cause the leaves turn this glucose into a red color. The brown color of trees like oaks is made from wastes left in the leaves.

     It is the combination of all these things that make the beautiful colors we enjoy in the fall.

1.The writer asked two questions in the beginning in order to        .

    A. persuade readers to believe something

    B. introduce the topic of the passage

    C. get the readers excited

D. offer something to think over

2. Which of the following is True according to the passage?

    A. Trees don't change colours with seasons.

    B. Trees can still perform photosynthesis well in winter.

    C. Trees have colours like yellow and orange even in summer.

D. Trees don't need food in winter.

3.Photosynthesis is a way that ___________________________.

A. plants change water and carbon dioxide into sugar

B. plants turn water and carbon dioxide into sugar with the help of sunlight

C. plants use glucose as food for energy and growing

D. chlorophyll is a great help

4. Which is the best title for this passage?

    A. Colorful trees in autumn            B. Mysteries of tree colors

C. Do you enjoy tree colors?           D. Wonderful colors in autumn

We all enjoy the beautiful show of colors as leaves change each autumn. But did you ever wonder how and why this happens? To answer the question, first you have to understand what leaves are and what they do.

Leaves are nature’s food factories. Plants take water from the ground through their roots. And they take a gas called carbon dioxide from the air. Plants use sunlight to turn water and carbon dioxide into glucose (葡萄糖). Glucose is a kind of sugar. Plants use glucose as food for energy and as a building block for growing.

The way plants turn water and carbon dioxide into sugar is called photosynthesis (光合作用). That means, “putting together with light”.

A chemical called chlorophyll (叶绿素) helps photosynthesis. Chlorophyll is what gives plants their green color. As summer ends and autumn comes, the days get shorter and shorter. This is how trees “know” to begin getting ready for winter.

During winter, there is not enough light or water for photosynthesis. Trees rest during this time and live off the food they stored during the summer. They begin to shut down their food-making factories.

The green chlorophyll disappears from the leaves. As the bright green fades away, we begin to see yellow and orange leaves. Small amounts of these colors have been in the leaves all along. We just can’t see them in the summer, because they are covered up by the green chlorophyll.

The bright reds and yellows we see in leaves are made mostly in autumn. In some trees, like maples, glucose is caught in the leaves after photosynthesis stops. Sunlight and the cool nights of autumn turn this glucose into a red color. The brown color of trees like oaks (橡树) is made from waste left in the leaves.

It is the mixture of all these things that makes the beautiful colors we enjoy during autumn.

36. Which of the following about chlorophyll is NOT true?

A. Without it photosynthesis couldn’t happen.

B. It is the reason why leaves have their green color.

C. It turns the leaves red during autumn.

D. It is a chemical that’s important for trees’ food making.

37. From the text we can see that photosynthesis _____.

A. can produce glucose, which can provide energy for trees’ growth

B. can happen whenever there is light and water

C. is the process of putting sunlight together with chlorophyll

D. doesn’t stop during the trees’ lifetime even in winter

38. What’s the author’s purpose of writing the passage?

A. To explain the process of trees’ photosynthesis.

B. To encourage readers to protect the environment.

C. To analyze the reasons why leaves change colors.

D. To help readers understand what leaves and trees are.

Plants can’t communicate by moving or making sounds, as most animals do. Instead, plants Produce volatile compounds, chemicals that easily change from a liquid to a gas. A flower’s sweet smell, for example, comes from volatile compounds that the plant produces to attract insects such as Bugs and bees.

Plants can also detect volatile compounds produced by other plants. A tree under attack by Hungry insets, for instance, may give off volatile compounds that let other trees know about the Attack. In response, the other trees may send off chemicals to keep the bugs away ——or even  Chemicals that attract the bugs’ natural enemies.

Now scientists have created a quick way to understand what plants are saying: a chemical Sensor（传感器）called an electronic nose. The “e-nose” can tell compounds that crop plants make When they’re attacked Scientists say the e-nose could help quickly detect whether plants are being Eaten by insects. But today the only way to detect such insects is to visually inspect individual Plants. This is a challenging task for managers of greenhouses, enclosed gardens than can house Thousands of plants.

The research team worked with an e-nose than recognizes volatile compounds. Inside the device, 13 sensors chemically react with volatile compounds Based on these interactions, the e-nose gives off electronic signals that the scientists analyze using computer software.

To test the nose, the team presented it with healthy leaves from cucumber, pepper and tomato plants, all common greenhouse crops. Then scientists collected samples of air around damaged leaves from each type of crop, These plants had been damaged by insects, or by scientists who made holes in the leaves with a hole punch（打孔器）. The e-nose, it turns out, could identify healthy cucumber, pepper and tomato plants based on The volatile compounds they produce, It could also identify tomato leaves that had been damaged. But even more impressive, the device could tell which type of damage ---- by insects or with a hole Punch ---- had been done to the tomato leaves.

With some fine-tuning, a device like the e-nose could one day be used in greenhouses to quickly spot harmful bugs, the researchers say. A device like this could also be used to identify fruits that are perfectly ripe and ready to pick and eat, says Natalia Dudareva, a biochemist at Purdue University in West Lafayette, Ind. who studies smells of flowers and plants. Hopefully, scientists believe, the device could bring large benefits to greenhouse managers in the near future.

We learn from the text that plants communicate with each other by____.

A. making some sounds        B. waving their leaves

C. producing some chemicals   D. sending out electronic signals

What did the scientists do to find out if the e-nose worked?

A. They presented it with all common crops.

B. They fixed 13 sensors inside the device.

C. They collected different damaged leaves.

D. They made tests on damaged and healthy leaves.

According to the writer, the most amazing thing about the e-nose is that it can___.

A. pick out ripe fruits

B. spot the insects quickly

C. distinguish different damages to the leaves

D. recognize unhealthy tomato leaves

We can infer from the last paragraph that the e-nose_____.

A. is unable to tell the smell of flowers

B. is not yet used in greenhouses

C. is designed by scientists at Purdue

D. is helpful in killing harmful insects

All sorts of items become litter(垃圾) but two of the most common and most dangerous are cigarette butts（烟头) and plastic bags. Litter is a big problem for our environment but it is a problem that individuals can easily do something about. Not littering at all or cleaning up litter, such as  cigarette butts and plastic bags, greatly improves the quality of our environment.

Although cigarette butts, are small, they are bad for the environment. Over 1,600 billion cigarette are smoked each year in China and large quantities of the butts are thrown away. Worldwide, about 4. 5 trillion butts are littered every year. Apart from the fact that butts spoil the beauty of the environment, they contain some very toxic chemicals. These find their way into the water supply where they decrease the quality of the water and endanger plants and animals that live there. So, if people have to smoke, they shouldn't throw away the butts but put them in the rubbish bin instead.

Plastic bags are another common form of litter that is a danger to the environment. There areseveral reasons for this. They are made from oil and gas, which are non—renewable resources. If they are not recycled, these resources are lost to us. In China, 2 billion plastic bags are used every day. An enormous number of these become litter. This is a huge problem because they last from 20 to 1,000 years in the environment. They float easily in the air and water and travel long distances. They find their way to rivers, parks, beaches and oceans. Plastic bags kill up to one million seabirds, 100, 000 sea mammals and countless fish each year worldwide. It is up to people not to let plastic bags become litter. It would be better if they used fewer and recycled them.

Cleaning up your cigarette butts and plastic bags would improve the environment. And we would know that we were doing something to look after our planet. However, I believe the best solution would be not to smoke or use plastic bags at all.

Which of the following best shows the structure of the passage?

A           B.         C.          D.

( ①= paragraph 1; ②= paragraph 2; ③= paragraph 3; ④a paragraph 4 )

The word “toxic” in the paragraph 2 most probably mean “________”

A. precious     B. extra    C.poisonous      D. useless

From the text. we know the fact that_________

A. Chinese smokers litter up to 4. 5 trillion butts every year

B. people in the world use 2 billion plastic bags in a single day

C. plastic bags cause 1 million deaths of seabirds each year worldwide

D. the butts can last 20 to 1,000 years in the environment of China

What's probably the best title of the passage?. Clean Up Your

A. Say Goodbye to Smokin   B. Protect the Endangered Sea Animals     . C.Use Paper Bags Now      D.Clean Up Your Butts and Bags