2 . The nature is full of mysteries. When autumn arrives in the United States and Canada, you can see one of nature’s, greatest scenes—the yearly migration (迁徙) of the monarch butterflies (帝王蝶).

No other butterfly in the world migrates like the orange and black monarch butterflies of North America. (A)Theycannot live for long periods in cold weather. So each autumn around October, the butterflies travel up to 3,000 kilometers south to (B) ________. Some even fly to the mountains of Mexico. Plenty of monarch butterflies almost block out the sky. And you can hear their wings beating.

The butterflies usually spend two months reaching Mexico. After five months of stay, they head back north in spring. But not one butterfly finishes the whole round-trip. They (C) ________ eggs along the way and die. Three generations of butterflies will live and die during the spring journey alone. The fourth and final generations of the year are born in early autumn. But the butterflies hardly rest before starting the long journey south again to Mexico. The most amazing thing about these monarch butterflies is that they always return to the (D) ________ trees in Mexico that their great-great-grandparents used the winter before.

What mysterious monarch butterflies! They remind us of our nation. Millions of people, generation after generation use their blood and lives to build up our happy life. So as teenagers, we should (E) ________.

3 . Zheng Xin is a firefighter. One day he was trying his best to control the fire of a burning house. Outside, he heard the cats crying. He couldn’t stop his work at the moment, but he decided to look for the cats after the fire was put (A) ________.

(B) took, a, control, long. it, time, to, the, fire. Luckily, no one inside was hurt. Then he began to find out where the cat noises were from. There was still a lot of smoke and heat coming from the building. He followed the cat noises to the sidewalk in front of the house. There were five scared baby cats crying together. They must have been inside the building, as their fur was badly hurt. Zheng Xin wanted to find the mother cat. Clearly, she had gone into the burning house and carried out all her babies, one by one-unbelievable.

He finally found her. Her paws and face were blackened, and her fur was burned all over. He could even see her reddened skin (皮肤) under the burned fur. She could hardly move. Zheng Xin picked her up and let her relax in his arms. He decided to save this brave mother cat and her (C) family.

The animal doctors told him they would watch the baby cats and their mother carefully, but they weren’t confident about the mother’s chances. They provided her with the best medical care. About a week later, Zheng Xin was excited that the mother cat would be alive. They named her Scarlet because of the color of her skin.

Zheng Xin was happy that Scarlet got together with the baby cats again. She touched each (D) ________ them, nose to nose. She risked her life and all of her babies were saved. As a firefighter, Zheng Xin sees heroic acts every day. But that day, what Scarlet showed him was (E) ________.

4 . I had two pets in my house, a dog named Sam and a cat named Katty. They loved each other so much that they were always together. When I played with one, the other joined in. If Sam barked at something, Katty ran to see what it was. When I took either one out of the house, the other was always waiting by the door when we returned. That was the way it was for years.

But one day, without any warning, Sam died of a heart attack （心脏病突发） at the animal hospital and I had to walk back to our house alone. This time, there was no Sam for Katty to greet and no way for me to explain why she would never see her friend again.

In the days that followed, Katty seemed heartbroken. She could not tell me in words how she felt, but I could see the pain and disappointment in her eyes whenever anyone opened the front door and the hope whenever she heard a dog bark.

As the weeks went by, the cat seemed to feel much better. One day as I walked into our living room, I happened to have a look at the floor next to our sofa where we had a statue （塑像） of Sam that we had bought a few years before. Lying next to it, one arm around the statue's neck, was Katty, happily sleeping with her best friend.

5 . Space vegetables are grown from seeds (种子). They have been taken to and brought back from outer space. The seeds are influenced by the radiation (辐射) and low gravity (重力) in outer space. When they are brought back to the earth, these seeds produce vegetables that are bigger, healthier and more nutritious (有营养的) than normal vegetables. People needn’t worry, because space vegetables are actually very healthy.

Here are some facts that you should know about space vegetables:

Space vegetables are grown from seeds (A)_________ are carefully chosen. After seeds are brought back from space, (C) they are tested to make sure that the vegetables they grow will be safe to eat. There are no traces (痕迹) of radiation after testing.

Space vegetables are better for you than normal vegetables. (B) _________ example, space tomatoes stay fresh for twenty days, which is one week longer than normal tomatoes.

After genetically modified (转基因) food came into the market, people worried that they were eating unknown things. Unlike genetically modified food, space vegetables have not been genetically changed. This means that no new genes (基因) are put into the vegetables. (D) So they won’t be bad for your health.

6 . Dinosaurs（恐龙）once lived on the earth for a long time. They suddenly disappeared millions of years ago. What happened to them？That's still a mystery. People never stop searching for the answer.

Some US scientists say it is because there were not enough male（雄性的）dinosaurs. They got this idea after researching crocodiles（鳄鱼）.

Mother crocodiles lay eggs and later baby crocodiles come out. The local temperature decides the sex（性别）of the baby crocodile. When the eggs are at a temperature of 26 ℃ to 30 ℃，the babies are all girls；when the temperature is 30℃ to 34℃，there are both boys and girls；when it is 34Cto36℃，only boys are born.

Dinosaurs' babies also came from eggs. So scientists have given us a new picture: millions of years ago，it suddenly became very cold. Almost all dinosaur babies were girls. There were fewer and fewer male dinosaurs. Mother dinosaurs could not give birth to more babies. Finally，these powerful animals disappeared.

Root Vegetables

Would you like to eat a root? You probably already have. People and animals eat many kinds of roots. ①Most roots that people eat are usually called root vegetables. A root vegetable is what we call veggies that grow underground.

A carrot is one type of root vegetable. It is the orange, edible root of the carrot plant. ②to, many, in, like, people, salad, put, it( . ) A turnip, is another root vegetable. It is a member of the cabbage family. Turnips are usually eaten boiled, steamed, roasted, fried, pickled, or even raw.

③Although some people do not consider potatoes to be a veggie, but they are a root vegetable. People like to eat them mashed, boiled, and fried. Sweet potatoes, yams, beets, and leeks are some other root vegetables that people like to eat.

The giant panda is one of the most popular animals in the world. A giant panda can grow up to 1.5 meters long and weigh up to 160kg. People think the giant panda is very lovely. ①　　1　　The WWF tells people about animals that they are in danger and raises money to save them.

The giant panda only lives in the wild in China. In the early 1980s, were only 1,000 left in the wild. The main reason why pandas are endangered is that the area where pandas can live has become smaller.

The WWF works to help giant pandas in the wild in many ways. One of the ways that helps them is to increase the size of panda reserves(自然保护区). Some reserves need to be joined together by planting bamboo between them to make “corridors”. These are paths that lead from one reserve to another. No one may harm the pandas in these areas. The corridors let pandas move from one habitat(栖息地) to another to look for food. ②　　2　　

Like other kinds of grass, a bamboo plant may be cut very low to the ground, but it will grow back very quickly. A Japanese scientist recorded one bamboo plant that grew almost 1.5 meters in 24 hours! Bamboo grows almost everywhere in the world except Europe. (2)There are more than 1,000 kinds of bamboo that grow around the world on both mountains and plains (平原).

Not all bamboo looks the same. Some bamboo plants are very thin. They may only grow to be a few centimeters wide while others may grow to more than 30 centimeters across. This plant also comes in different colors, from yellow to black to green.

Many Asian countries have been using bamboo for hundreds of years. They often use bamboo for building new buildings. As a matter of fact, the cables (绳索) that hold up the hanging bridge across the Min River in Sichuan are made of bamboo. The bridge has been in use for more than 1,000 years, and is still holding strong.

In Africa, (3) engineers are teaching poor farmers how to use bamboo to find water. These African countries need cheap ways to find water because (4) they have no money, and their fields often die from no rain and no water. It seems that bamboo is one of the best things they can use. Bamboo pipes and drills (钻) can help to make the poor thirsty fields be watered.

10 . When we talk of plants, most of us will think of things that grow from the ground and have green leaves, but there are plants that do not look or act like other plants. Some of these belong to a special class of plants called fungi.

Fungi may appear almost everywhere. ①________________________Because fungi do not have green leaves to make their own food, fungi must take their food from animals, other plants or water. Some fungi live on dead or rotting wood, while others grow on living trees or in dirt or moss(苔藓). Mushrooms(蘑菇) are the best-known fungi.

②___________________For example, cauliflower mushrooms are found in forests from July to October. They can grow to be as heavy as fifty pounds! They grow at the foot of trees. Squirrel’s bread(松茸) is another kind of wild mushroom. Its appearance and use can explain its name. These fungi look like small golden cakes. Squirrels can easily eat them or carry them off to their hole to eat later.

③食品店里的蘑菇是人们精心种植的，可安全食用。People are warned never to touch or taste wild mushrooms, because some of them are deadly. Even less dangerous ones can still make a person very sick.