The ocean can be a great place to swim and play, it may also be useful in another way. Some scientists think that waves could help make electricity.
   “Have you ever been on a surfboard or boat and felt yourself being lifted up by a wave?” asked Jamie Taylor of the Wave Energy Group in Scotland. “There is certainly a lot of energy in waves.”
   Scientists are working on using that energy to make electricity. The United States and a few other countries have started doing research on wave energy, and it is already being used in Scotland.
   Most waves are created when winds blow across the ocean. “The winds start out by making little ripples (波纹) in the water, but if they keep on blowing, those ripples get bigger and bigger and turn into waves,” Taylor said. “Waves are one of nature's ways of picking up energy and then sending it off on a journey.”
   When waves come towards the coast, people can set up dams(大坝) to block the water and send it through a large wheel called a turbine(涡轮). The turbine can then power an electrical generator(发电机).
   We will never run out of wave power. Besides, wave energy does not create the same pollution as oil and coal do.
   Oceans cover three quarters of the earth's surface. That would make wave power seem perfect for creating energy around the world. But there are some disadvantages that need us to pay more attention to.
   Jamie Taylor said that wave power still cost too much money. He said that its influence on animals in the sea is still unknown. Besides, wave power would get in the way of fishing and boat traffic.
   With more research, “Many of these problems might be solved,” Taylor said. “Finding more energy sources(资源) is very important, for traditional sources of energy like oil and gas may run out some day.”
   In the future, when you turn on a light button, an ocean wave could be providing the electricity!

    How long is a year? Most people say a year is 365 days. It takes about 365 days for the earth to go around the sun. In fact, it takes a little longer for the earth to go around the sun. It needs 365 days, 5 hours, 48 minutes, and 46 seconds.

    If a year has only 365 days, what happens to the extra(额外的) 5 hours, 48 minutes, and 46 seconds? The answer is this: Every four years, we have another day. It's February 29, and we call this day " a leap day(闰日)".This kind of year is called "a leap year". A leap year has 366 days.

People born on February 29 are called leap-day babies, or leapers. There are about four million leapers in the world. When do they celebrate their birthday? Do they celebrate only once every four years? Some leapers celebrate the birthday on February 28, and others celebrate it on March 1. Think about it: A twelve-year-old leaper may have celebrated only three birthdays on the real day after he or she was born!

    Which year are leap years? Years that can be divided(除尽)by four are leap years. The year 2000 was a leap year. Then 2004,2008,2012,2016 were the next leap years. If you know a leaper, you must say "Happy birthday!" to him or her on the leap day, because you just have one time to do that every four years!

    What was discovered by accident? The answer is penicillin (青霉素). It kills germs. By killing germs, it saves lives. Suppose you are sick. You go to a doctor. She examines you. She says you have a "staph" infection (葡萄球菌感染). She gives you some medicine. You take it. The medicine knocks out the staph. Soon you are well. Before penicillin, this would not happen. Staph was almost sure death.

    Everyone wanted a medicine. Laboratories worked day and night. They grew the staph in small dishes. Then they tried to kill it. Nothing worked.

    The laboratory dishes had covers on them. They kept things from falling into dishes. Molds (霉菌) were a big worry. They are always in the air. You can't see them. They're too small. There are thousands of different molds. Molds can make an experiment fail. That's why dishes are covered.

    Dr. Alexander Fleming was working to kill the staph germ. He worked for years. One day he took a cover off a dish. He looked inside. There was a thick growth of staph germ. There was also some mold. Then he saw something strange. Where the mold was, there was no growth of staph. This is what Fleming probably thought. "By accident, I found a mold to kill the dreaded staph."

    This is how penicillin was found. But here's the real miracle. There are thousands of kinds of molds. But only one kind can kill staph. The mold must have fallen into the dish a few days before. The cover was probably off only a few seconds. In those few seconds the right mold fell into the right dish. Another man might have thrown the dish away. But Fleming was very careful and smart. He understood what the mold did. How lucky the humans were!

    Waste can be seen everywhere in the school. Some students ask for more food than they can eat and others often forget to turn off the lights when they leave the classroom. They say they can afford these things. But I don't agree with them.

    Waste can bring a lot of problems. Although China is rich in some resources(资源), we are short of others, for example, fresh water. It is reported that we will have no coal(煤) or oil to use in 100 years. So if we go on wasting our resources, what can we use in the future and where can we move? Think about it. I think we should say no to the students who waste things every day. Everybody should stop wasting as soon as possible.

    In our everyday life, we can do many things to prevent waste from happening, for example, turn off the water taps when we finish washing, turn off the lights when we leave the classroom, try not to order more food than we need, and so on. Little by little, everything will be changed. Waste can be stopped one day, if we do our best.

    Mint (薄荷) is a useful plant. You can see it in different kinds of dishes. Mint can bring us many health advantages. It can also help us relax. Don't you believe it? Just smell the plant when you feel tired.

    Now, if you love mint, you don't have to buy it at the market. The plant is very easy to grow. You can plant it all year round, and it can grow well both indoors and outdoors.

    ①Prepare your flower pot (盆)

    Fill your flower pot with soil. Fill soil to a depth (深度) of about 25 centimeters. Use a garden fork to loosen the soil (松土).

    ②Plant your mint

    Plant your mint seeds (种子) 40 centimeters far from each other. If your pot is small, use just one plant or seed.

    ③Put your plant in a proper place

    Mint loves sunlight, but it also likes a bit of shade. Put your plant in a place where it can get both sunlight and shade.

    ④Water your mint

    Mint prefers wet soil. Keep the soil well watered, but don't overdo it. Don't forget to put a plant plate under your pot.

    ⑤Time to harvest

    Mint grows fast. After your plant grows up, you can pick its leaves at any time.

    To make things more fun, why not ask each of your classmates to grow some mint? Let's see whose mint grows the fastest!