Do you know why different animals or pests have their special colours? Colours in them seem to be used mainly to protect themselves. Some birds love eating locusts (蝗虫), but birds cannot easily catch them, why? It is because locusts change their colours with the change of the colours of crops. When crops are green, locusts look green. But as the harvest (收获) time comes, locusts change to the same brown colour as crops have. Some other pests with different colours from plants are easily found and eaten by others. So they have to hide themselves for living and appear only at night.

    If you study animals' life, you'll find the main use of colour is to protect themselves. Bears, lions and other animals move quietly through the forests and they cannot be easily seen by hunters. This is because they have the colours much like the trees.

    Have you ever noticed an even stranger act? A kind of fish in the sea can send out a kind of very black liquid (液体) when it faces danger. While the liquid spreads, its enemies cannot find it. And it immediately swims away. So it has lived up to now though it is not strong at all.

    In America, the school day usually starts at 9 a.m. and finishes at about 4 p.m. The school subjects are different from1. In China, we always2Chinese, math, English, P.E. and so on. But in America, students have more3, such as cooking and driving lessons. Their school life isn't just4study. They also have more things to do than（比）Chinese students. There are many clubs（俱乐部） in American schools, 5. If the students are interested in sports, they6join different sports clubs. American students also have art clubs, language clubs and some7clubs. From 2:30 p.m. to 4 p.m., they do8things in these clubs.

    Maybe you think English is very popular in the world, so American students don't need to 9any other language.10that's not true. American children from the age of seven have to learn a foreign language. For example, they learn French or Chinese.

    How green are you? Do you know how to be green?

    We all need a healthy environment, but we produce waste every day and it does harm to our environment. Though we are young, we can still do something to help. In fact, even the simplest everyday activities can make a real difference to the environment. Here are some ideas for you.

    Reduce

    Reduce means "use less". Don't waste things. This saves money and reduces pollution and waste going into the environment. Before we buy something new, think whether it is really necessary—or maybe the old one will be just as good! When we buy things, choose local products if possible, and try not to buy too many things from abroad.

    Reuse

    Reuse means "use again". Use things for as long as possible. When we buy things, make sure that they last a long time. We should look after them so that they will last, and we should repair them if we can instead of throwing them away and buying new ones. Don't use a paper cup or a paper bag. It's better to use a china (瓷器) cup and a lunch box because you can use them again.

    Recycle

    Recycle means "change things into something else". Though it takes energy to change something into something else, it's better than throwing things away or burning them. Find out what can be recycled in your neighbourhood and take part in recycling programmes. We should also buy products made from recycled materials, such as recycled paper, to help save trees.

    So please remember these three words: reduce, reuse and recycle.

①Eating good food and getting proper exercise are important to stay healthy. Getting enough sleep is important, too. Experts say that teenagers between the ages of 15 and 20 need 8 to 10 hours of sleep each night. 

②Your body needs to take a rest from all the activities it has done during the day. Your brain needs a rest, too. You are likely to get sick easier without enough sleep. 

③You have a "24-hour clock" inside your body that tells you when to be awake and when to go to sleep.  ▲  Blue light that comes from the Sun tells your brain to keep you awake during the day. When there is no blue light at night, the brain tells the body that it's time for sleep. 

④There are many things that stop the brain from telling your body when it's time to sleep. One of these is blue light at night. Today, people spend a lot of time watching television or looking at screens on computers or smart phones. These devices (装置) give off blue light. If you look at them at night, the blue light can trick your body into thinking it's daytime. Then it is more difficult to go to sleep.

⑤What should you do to get good sleep? Experts say that you shouldn't look at screens that give off blue light for at least one hour before going to sleep. 

⑥ Do not watch TV or use anything with a computer screen in bed. If you need to do something to fall asleep, it is better to read a book. Also, keep your bedroom as dark as you can. This will help you sleep well. 

It was a cold winter morning. My 12-year-old granddaughter, Jayne, sent me messages on the phone every hour during her six-hour drive to our house.

"Grandma, can you put some snow in the fridge (冰箱)? That way, I can feel snow when I get there," she wrote. Jayne lives in the south of Georgia, the US with her parents, so she never saw snow before.

"Yes, I will," I wrote. "There is still some snow on the ground in the yard." And I sent her a few photos of it. However, the weather report brought me bad news. It said the weather would be sunny at noon. This made me feel concerned.

In the afternoon, they finally arrived. Jayne got out of the car first. She ran into the yard and put her hands in the snow. She looked so excited. It was great that the sun didn't come out that day.

"Grandma, the weather is so cold, but I enjoy playing with snow," Jayne said. Then she started to build a snowman. She made two large snowballs first. They were the head and the body. It looked nice. Jayne kept playing outside until her hands got wet and cold. Watching Jayne playing in the snow made me feel warm and thankful.

I still remember the lovely cold day. Small things in our lives can also make us happy.