阅读下列短文，从每题所给的A、B、C、D四个选项中选出最佳答案。

    All living things need energy to live and grow. This energy comes first from the sun. Plants use water and sunlight to make their own food. Animals can not make their own food, and they eat plants. Other animals then eat the plant eaters.

    A food chain shows what eats what. It might show that zebras eat grass and then lions eat zebras.   

    Lions also eat other animals. Zebras eat other kinds of plants. So it takes more than one food chain to show how lions and zebras get their energy.

    A food web shows how food chains work together. From it we can see how energy moves from plants to animals.

    Plants and animals that live in hot, dry deserts depend on water as well as food. Creosote bushes have small leaves that hold water. Their seeds provide food and water for kangaroo rats. Kangaroo rats don't need to drink water. They get all the water they need from the plants they eat. Kangaroo rats keep cool by coming out only at night to look for food. Ringtail cats also come out only at night. Ringtail cats hunt and eat kangaroo rats. Coyotes eat both the kangaroo rats and the ringtail cats.

    Nothing is wasted in a food wed. Vultures eat dead animals. Vultures are scavengers. Scavengers do not hunt and kill other animals to get food. They eat animals that are already dead. When a ringtail cat or a coyote dies, it makes a meal for the vultures. Scavengers do an important job in keeping the environment clean.

    Thousands of years ago,in the south of ancient China,there lived Shennong,a man who had an ox head and human body.Seeing that local people were suffering from disease,he built ladders and houses on a high mountain to store hundreds of medical plants.To remember him,people named the place shennongjia.

    The legend(传说）makes Shennongjia in Hubei an inciting place for tourists.Traveling there is a unique experience,as you can see sceneries of the four seasons from different altitudes(海拔）.“When the bottom of the mountain is summer,the top is spring and while the foothill is autumn,the top is covered with ice,”local people say of the special climate of Shennongjia.

    Shennongjia is also home to 5,000 species of animals and plants.Many animals in danger live there,such as the golden monkey,the clouded leopard and the Asian black bear.

    One interesting and mysterious(奇妙的）thing about Shennongjia is its legend of wild men.Some people once claimed that they saw big prints or big-foot creatures.Yet so far,scientists haven't proved it is true and some say they are just bears.

    The beautiful place has recently received a new title.On July 17,2016,Shennongjia Forestry District was added to United Nations World Heritage list as a natural site.Chins now has 50 world heritage sites(遗址），second only to Italy in the world.

    The spring season brings warm weather, flowers and other changes for people to enjoy. For some restaurant cooks, the most exciting spring arrival is ramps.

    Ramps are a wild plant in the eastern mountains of North America. They are one of the first plants that grow in the spring, usually between April and May. They are recognized(意识) by their red stem(茎), and two long and wide green leaves. They are also famous for their strong taste, similar to onions(洋葱).

    Ramps are not as well-known as other vegetables, but they have a long history in the United States. In the Appalachian Mountains, ramps have been an important food for a longtime. During spring, it is common for small towns in the Appalachian area to hold large ramp dinners for the community.

    However, over the last 30 years, ramps popularity has grown quickly. They are now a highly-desired vegetable for many nice restaurants in cities like New York and Washington D.C.

    One reason the plant is popular is that it grows in the wild. It is difficult to grow them on farms. Most restaurants get them from foragers, who collect ramps by searching forests for some small pieces of land where they grow. Ramps have a short season. Within a few weeks of full growth, the plant is done for the year. This shot life is some reason for their popularity.

    And that popularity could lead Io their disappearance from Earth. In 1995, the local government in Quebee, Canada, stopped people selling the plant to businesses in order to protect the plant against being over-dug.

    The season is short, but it has not ended yet. If you are in the right place, you still have time to try a taste of ramps yourself.

根据材料内容选择最佳答案。

    You can not see any object unless light from that object gets into your eyes. Some of the things you see give off light of their own. The sun, the stars, a lighted lamp are examples that can be seen by their own light. Such things are luminous. Most of the things you see are not giving off light of their own. They are simply reflecting light that falls on them from the sun or some other luminous bodies moon. For example, does not give off any light of its own. It is non-luminous. You see it because sunlight falls on it and some of it reflects in our direction. So moon light is only second hand sunlight.

    When you look at a book, it sends to your eyes some of the light which falls on it, and you see the book. If light could be kept out from where you are so that there would be no light for the book to reflect, then you could not see the book even with your eyes wide open.

    Light travels so fast that the time in which it travels from the book you are reading to your eyes is so short as if there were no time at all. Light reaches us from the moon, which is about 380 000 kilometers away, in only a little more than a second.

    The population of the world is still going up and scientists are worried that there will not enough food for us in the middle of the century. One plant from Madagascar, the Kalanchoe fedtschenkoi, may help. It takes in carbon dioxide (二氧化碳) at night and it needs 10 times less water than food plants like rice. This means it can grow in the desert(沙漠).

    It is dangerous to eat this plant, but scientists can study two things about it: how it takes in carbon dioxide at night when other plants only do this during the day, and why it is so good at living in the desert. There will be less good land for growing food in the future because deserts are increase in size. There, growing plants will be more and more important.

    There is a possible way to take this research. To grow a desert plant to eat will be difficult, but it may be possible to use the genes(基因) from this plant and put them into food plants like beans or potatoes. And the food plants with the genes can grow in the desert. We hope the plant could be an answer to our future food.