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    There is good and bad news about the number of trees on out planet. The good news is that there are seven times more trees for everyone than we thought.

    A few years ago, scientists believed that the world bad 400 billion（十亿）trees. However, a new study from Yale University shows that there are around three trillion（万亿）trees. Thatmeans a three followed by 12 zeroes. That means there are about 420 trees for everyone in the world today.

    The bad news is that thousands of years ago, the earth had six trillion trees. Humans cut in half the number of trees on the planet. Take Europe for example, it was a large forest thousands of years ago. Now much of it is cities and towns. And another 15 billion trees are lost each year.

    Dr. Thomas Crowther is one of the scientists from Yale University. He said the new number of trees from their study would change nothing. " The study only shows we need to do more to protect our forests." He said.

    People already know a lot about animals. However, there are still some things about animals that may surprise you. Here are some facts about animals you probably didn't know.

    Cows do have best friends and feel stressed when they are separated. Scientists have found that cows are very social animals and a cow always makes friends with other cows. When a cow is with its friends, it feels relaxed, compared with when it is alone.

    During breeding season, a male penguin (企鹅) will offer a small stone to a female penguin as a gift. If she takes it, they will become partners. When the female penguin lays an egg, she and her partner may carry it on their feet, because some penguins don't build nests (鸟巢).

    Crocodiles (鳄鱼) swallow (吞) stones. Crocodiles always swallow their food instead of eating it like other animals. They swallow stones which break the food into very small pieces in their stomachs. These stones may stay in their stomachs all their lives.

    Elephants use plants to treat pain or other illness. Scientists once found a pregnant (怀孕的) elephant in Africa who ate a kind of plant which was not part of her normal food. Four days later, she gave birth to a baby elephant. The same plant was used by the local pregnant women.

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Life in 2060

    Let us suppose the life in A. D. 2060. It is fifty years later. Of course, things have changed and life is very different. Voyages to the moon are being made every day. It is as easy to take a holiday on the moon today as it was for the people in 1960 to take a holiday in Europe. At a number of scenic spots on the moon, many hotels have been built. The hotels are air- conditioned, naturally. In order that everyone can enjoy the beautiful scenery on the moon, every room has at least one picture window. Everything imaginable is provided for entertainment of the young and old. What are people eating now? People are still eating food. They haven't yet started to take on heir(继承) supply of energy directly like electrical current or nuclear power.

    But many foods now come in pill forms, and the food that goes into the pill continues to come mainly from green plants. Since there are several times as many people in the world today as there were a hundred years ago, most of our planet's surface has to be filled. The deserts irrigated with water and crops are no longer destroyed by pests. The harvest is always good. Farming, of course, is very highly developed. Very few people have to work on the farm. It is possible to run the farm by just pushing a few buttons now and then. Such would be our life in 2060.

    One day, you open the fridge and find some moldy (发霉的)food. But before you can throw it away, your mother stops you. She doesn't want to waste food. She cuts off the moldy part and eats the rest. Is it safe to do this?

    Mold (霉菌)can grow on almost all kinds of food. Mold is usually green, white, black or grey. Mold makes food soft and changes its color. Moldy food tastes quite bad一一and it's not safe to eat.

    If you find mold in soft food, just throw it away. Soft food, such as bread, tomatoes or hot dogs, usually contains water. This allows mold to easily grow below its surface. Bacteria (细菌)can also grow along with it.

    But it's easy to remove mold from hard food. The mold can't grow very deeply inside this kind of food. According to the BBC, you should cut about 2.5 cm around and below the mold to remove it. It's OK to cut the moldy parts out of hard food and eat the rest. But if the food is completely covered with mold, you should still throw it away.

    Most kinds of mold are bad for us. But some kinds of mold can be used to make food. For example, penicillium (青霉菌)can be used to make many types of cheeses, such as blue cheese. These cheeses are safe to eat--and they're quite delicious as well.

    As space science develops, man has learned more and more about space. Space is not only amazing but also dangerous. While working in space, spacemen are facing danger as well as success.

    Scientists have found out that the radiation(辐射) is the greatest danger to spacemen in space. When spacemen are working in space, they are in danger of the radiation from the sun and other stars, which is bad for their health. The harm of the radiation won't be found until their children even grandchildren are born. Some special medicine may work a little, but no really effective medicine has been found so far.

    Space rubbish is also thought to be a great danger to spacemen. It's reported that there were 9,000 man-made things flying in space. About 30% of these are satellites, 10% are spaceships, and the rest are space rubbish. An explosion(爆炸) in space in 1999 made a cloud of 300,000 fragments, each at least 4 mm in size. A small piece of these even knocked a spaceship window and caused some damage(损坏). Scientists are watching and reporting any possible danger all the time. They are working to deal with space rubbish.

    Although space is really dangerous, it interests many people on the earth. In the near future, it may become possible for people to spend a few days in a space hotel. We may even choose to leave the earth and live in space in a few years. So we should do something to help improve the space environment.