【推荐1】Do you believe stones can move by themselves? There are some stones that can move in Death Valley of the USA. Many of the stones are small, but a few of them are big. The biggest stone weighs about 350 kg.

The stones only move at night. Nobody has seen them moving, but now scientists know why the stones can move. The answer is the wind. When the wind comes from the west, the stones move to the east(东). When the wind is from the south, they always move to the north. But how can the wind move the heavy stones?

Death Valley is one of the hottest places in the world, but it can be very cold at night. Sometimes, there are even storms at night. Rain falls, and the wind is strong and cold. The water on the ground turns into ice(冰) easily. Then the strong wind can move the stones along the flat(平的) ground. In the morning, the sun comes up and dries the ground. Then people can find the stones move from one place to another in the daytime.

【推荐2】Are you interested in science? How do you think scientists usually make new discoveries? The world produces millions of tons of plastic wastes every year. What do you think the best way to deal with plastic pollution is? Why?

Caterpillars(毛虫) are often used as food for fishing. However, they are now set to join the war on plastic wastes.

Fcderical Bcrtocchini is a scientist with the Spanish National Research Council. When she's not working in her lab, Bcrtocchini keeps bees. One day, when she looked at her beehives(蜂箱),she found lots of caterpillars which were called waxworms(蜡虫). They are often used to feed fish. In the wild, however, they live in beehives, feeding on the wax that bees use to build their houses. Bcrtocchini picked out the caterpillars and put them in a plastic bag. Surprisingly, when she returned to the bag after cleaning out the hives, she (bund it fill! of holes. The worms had eaten their way out.

Bcrtocchini doesn't study plastic. However, you can't keep a good scientist away from an interesting question: Were the waxworms digesting(消化)the plastic?

Bertocchini got in touch with Paolo Bombeli and Christopher Howe at the university of Cambridge. According to their paper, some chemicals within the insects can really break down plastic.

Other scientists have also discovered plastic-eating species(物种). In 2016, for example, a Japanese team found a bacterium(细菌). The bacterium has to spend more than six months eating a layer(层) of plastic bag. However, Bertocchini and her partners discovered that it took a waxworm about 12 hours to eat a layer of plastic bag.

Butthe scientists reminded that it would be at least several years before they set free waxworms into the environment. They want to know if the waxworms are using the plastic as a food, or just they want to run away. If they just want to run away they are going to get fed very soon. But if they want to eat it as food, it's a completely different game.

"It's certainly not going to be the case that within six months we've solved the world's plastic problem, said Howe. "I wouldn't want people to think that within a few months, they can start throwing away plastic bags without worrying about it. "

【推荐3】Why don’t birds get lost on their long flights (飞行) from one place to another? Scientists have studied this puzzle for a long time. Now they’re starting to fill in the blanks(空白).

Not long ago, experiments showed that birds use the sun to guide them during daylight hours. How do birds fly at night? Tests with artificial stars, which are made by people, have proved that certain night-flying birds are able to follow the stars in their long-distance flights.

They found a bird that spent its lifetime in a cage and never flew under a natural sky. But it was born with the ability to use the stars to look for the direction. This bird’s cage was placed under the sky filled with artificial stars. Any change in the position of the artificial stars caused a change in the direction of the bird’s flight. From the experiment, they found that the bird tried to fly in the same direction as those artificial stars moving under the natural sky.

But the stars are of course birds’ main ways of navigation (航行), when the stars are hidden by clouds, they can still find their way by such landmarks (路标) as river courses, mountain ranges (山脉), coast lines and so on. Because of this ability, people use the dove (鸽子) to send messages in some fields. For example, the doves were used to send messages in both World War I and World War II. During that time, thousands of doves were used to carry important messages in order to save the lives of many thousands of people. So it is also the symbol of peace.

But when it’s too dark to see these things, the doves are not able to find their way. They only circle helplessly and get lost.

【推荐2】Most people love animals because they are useful in many ways. They add(增添) more fun to our life.

We find many different kinds of animals on the earth. Some animals, such as leopards, wolves, pandas and foxes live in big forests. They are called wild(野生的) animals. Most of them are dangerous. Some of them are afraid of people. We can only watch them in the zoo. Some others like cows and dogs live with men. They are called domestic(家养的) animals.

Animals are important to men. Men catch wild animals for fur and meat. Skins(皮肤) of foxes and crocodiles can be made into coats and shoes. People are now stopped from killing wild animals in order to protect(保护) their lives. Domestic animals can not only give men food, but also help men with some farm work. Without them life could be less fun and more difficult. People get meat from sheep and pigs. From cows, we get milk. Horses can take us to other places. On farms, animals are used to plough fields(耕田).

It is clear that men can’t live without animals. Let’s protect animals. They are our best friends.

What would happen if you tried to blow a soap bubble in below-freezing (低于冰点) weather? Would it freeze and fall to the ground? Would you have to hit it with a stone to break it? These questions came into my mind one cold winter day. It was too cold to play in the snow, but it was a perfect time to experiment with blowing frozen bubbles.

To blow frozen bubbles, I had to wait until the air outside was very cold. For this activity, that meant -10℃ or colder. I didn’t have the bubble things so I used dish-washing soap. I chose a place out of the wind, and blew bubbles the same way I always do. I watched to see what would happen. Here’s what I learned.

If the temperature is low enough, the skin of the bubble frosts (结霜) over, becoming cloudy instead of clear. And what about those rainbow swirls (漩涡状物体) that you see in soap bubbles? The rainbow colors stay the same shape when the bubbles frost, but they don’t spin (旋转) anymore. The bubbles still float in the air. They don’t fall to the ground any faster than they would on a warm summer day.

When these frozen bubbles break, they don’t turn in to tiny drops of soap as summer bubbles do. They turn into shiny rainbow pieces and fly slowly to the ground. Sometimes a frozen bubble will roll across the snow without breaking. If it breaks, it may leave a strong bubble skin on the ground. Leave the bubble alone and it may stay there for a long time. Sometimes I could catch a bubble and hold it until the heat of my hand made it break.

I learned one other thing about blowing frozen bubbles. It’s so much fun. I want to try it again next year!

【推荐1】It was a warm April day when a big fat envelope came in the mail from the only college I had ever imagined attending. My eyes were fixed on the word "congratulations". I don't remember ever smiling so wide.

Then I looked at my financial (财政的) package. The cost of Dream School's tuition (学费), room and board was around $ 40,000-an impossible number! How could I afford to attend? What good reasons did I have to go there when three other fine colleges were offering me free tuition? My other choices were good, even if they weren't as famous as my first choice.

In my mind, attending my dream university would be the only way to realize my dream of becoming a world-class writer. My parents understood how I felt. They told me that even though it would be a financial problem, I could go wherever I would be happiest. But as I was always careful with money, I wasn't sure what to do.

One of the schools that offered me a full ride had an informational dinner one night in the spring. Considering my parents' difficulties, I decided to drive the 45 minutes and attend. At first, all I had planned to do was smile politely, eat free food, listen quietly. But I surprised myself.

At dinner the president of the university talked about the wonderful activities at school including guest lectures and social gatherings. He also made it perfectly clear that free food would be offered at all future events. He continued with explanations of professors, class sizes, activities, and sporting events at school. As he spoke, I began to realize that this school, though not as good as my first choice, might be the best one for me. It seemed small yet with many great programs. It seemed challenging yet caring.

After that I walked out that door, a feeling of comfort washed over me. Looking at the campus that night, I realized that I would be spending the next four years right there.

In all honesty, my university is not as well-known as my "dream" university. However, it turned out to be the right choice of schools for me.

【推荐2】It was a sunny Sunday afternoon. I stopped at a teahouse to enjoy a cup of tea. Suddenly, I felt a hand on the back of my jacket and heard someone say, “Hi, David! How are you doing?”

Looking back, I saw a man. He looked familiar, but I couldn’t remember where we had met.

The young man also held a cup of tea, so I asked him to join me. Very soon, his story began to evoke my memory.

His name is Peter. Six years earlier, Peter was driving back home late on a February night. A heavy snow had arrived that afternoon, and by midnight, the snowdrifts (雪堆) were getting deep. His car was stuck in a snowdrift just down the road from my house.

He walked to my house for help. I helped him pull his car out of the snowdrift and up to the street where the snow had been cleaned away.

This was a normal happening here during the winter. I couldn’t count the times someone has helped me to pull my car from a snowdrift. However, it was an unforgettable experience for him. He was only eighteen at that time, and he said he was very afraid. No one wants to be stuck in a snowdrift at night.

Sometimes, one simple kindness at the right moment can change the direction of a life. So, be kind and helpful.

【推荐3】Peter Tabichi is 37 years old. He is from Kenya, Africa. He is a math and science teacher. His school is in a poor area. It’s small, but the classes are very big-there are about 58 students for every teacher. The school has only one computer. But Mr. Tabichi always makes his classes interesting and helps his students study well. He is kind and friendly to his students. His students say he is like a father to them.

Mr. Tabichi comes from a family of teachers. He doesn’t just work on school days. He also works after school and on weekends to give students extra（额外的）help. He goes to the students’ homes and gives them more help. He really likes his job.

In 2019, Mr. Tabichi got the Varkey Foundation Global Teacher（瓦尔基基金会全球教师奖）. He gives lots of his money to help his students and other people.

【推荐1】When you want to go shopping, you will decide how much money you can pay for new clothes and think about the kind of clothes you really need. Then you just only look for those clothes. There’re labels（标签）inside all new clothes. The labels tell you how to take care of your clothes. The labels may say “dry-clean only”. If you put these clothes into the water to wash them, you may ruin（损坏）them.

Many clothes today must be dry-leaned. Dry-cleaning is expensive. So when you buy new clothes, check if they will need to be dry-cleaned. You’ll save money if your clothes can be washed in water.

You can also save money if you buy clothes that are well-made. Well-made clothes last longer. They look good even after they have been washed many times. Clothes that cost more money are not always made better. They don't always fit better. Sometimes the less expensive clothes look and fit better than the more expensive ones.

【推荐2】It might seem impossible that tiny insects could be very harmful to a large house. But wood-eating termites（白蚁） can indeed do a lot of harm to a house.

Scientists believe that termites have been around for about 50 million years. Today, there are nearly 3,000 kinds of termites. They can be found all over the world.

A termite’s diet is mainly made of the fiber（纤维素） found in plants. Many termites feed on trees and wood in wooded areas. However, they don’t know the difference between the wood in a forest and the wood used to build houses. If they find wood inside a house, they will happily eat it.

It would take a single termite over 3,000 years to eat up the wood in a small house. Unluckily, termites are social insects. They live in groups. A termite group could be made up of 15 million termites or more. They eat day and night. Large termite groups can eat as much as one pound of wood in a day.

Termites can be hard to discover. Often, they’re found only after big damage has been done to a house, especially in May every year.