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.

    When you're closing your eyes and hitting your pillow, you're probably not giving much thought about the sleeping position throughout the night. Most people don't change their sleeping positions throughout their lives. The following is why you might want to pay more attention: Your sleeping position can actually say a bit about who you are and what your personality is like.

    There are many sleeping positions. The fetal (胎儿的) sleeping position is generally the most common sleeping position. Fetal sleepers sleep on their side, they move into a position in which their body makes a rounded shape. People who sleep in the fetal position are often quite sensitive and generally shy. They are often worried or nervous and don't focus their attention on the main problem, but get into trouble on very small pieces of information.

    The log (木头) sleeper rests on the side with a straight body when hands and legs are kept at the sides. These sleepers are often relaxed, but also can easily believe lie-tellers. If you're a log sleeper, you might want to keep in mind that it's good to be easy-going and have less stress, but don't be so quick to go with the flow (流) at all times.

    The third one is the soldier position. Soldier sleepers typically lie on their backs with both arms close to their sides. In general, they are the strong and silent type. However, they can also put the pressure on. "They can be quite strict with themselves as well as others," a scientist added.

    Water is very important to us. Every day we drink water, cook with water, take a shower in water, and have many other activities with water. Let's read and learn more about it!

    70percent of an adult's body is water. And about 80percent of a baby's body is water.

    Drinking too much water q{#blank#}1{#/blank#} can cause water intoxication (醉).

People should have about eight c{#blank#}2{#/blank#} of water every day.

    By the time you feel thirsty, your body has l{#blank#}3{#/blank#} over one percent of its water.

    About 80percent of the Earth's surface is covered with water.

    Only one percent of this water is fresh, 97percent is salt water and two percent is f{#blank#}4{#/blank#} in glaciers (冰川).

    And now, it's time to s{#blank#}5{#/blank#} water!

    A new rubbish sorting system (垃圾分类系统) has been put into use in Fangchengyuan Community in Beijing. Local people not only sort their rubbish, but also put QR codes (二维码) on it.

    "When the rubbish is collected and the codes are seen, I will get reward points to exchange for small gifts and even some money," one of the local people told reporters. "It's really creative and encouraging."

    This smart system has been carried out in 350 communities in Beijing. The capital of China has joined a list of cities in the country that take action to support rubbish sorting. For example, Shenzhen and Shanghai have made laws to punish people and organizations for not sorting rubbish correctly.

    China produces quite a lot of rubbish every year. Much of the rubbish is buried (填埋) in soil or burned without being sorted. Landfills (填埋场) take up a lot of land and have a risk of polluting the soil and water nearby. And burning rubbish can produce harmful gases. Through rubbish sorting, we can reduce the use of landfills and air pollution.

    What's more, rubbish sorting saves resources, which could bring economic benefits (经济利益). For example, a ton of waste paper can be reused to make about 850 kg of paper, saving 17 trees and 50 percent of water. Because of the benefits, some countries have developed successful sorting systems.

    Japan has a strict and detailed system. When people throw away a water bottle, the cap, the wrapper (包装纸) and the bottle itself have to go into three different bins. Every year, families receive special rubbish sorting timetables and directions from their local governments. They are advised to follow the timetables and directions when they throw away rubbish.

    In Australia, every family is provided with three rubbish bins—the red lid (盖子) bin for "general waste" like food and plastic bags, the yellow lid bin for "recycling" like steel and glass, and the green lid bin for "green waste" such as grass and leaves. On the streets, the bins are printed with pictures of the things that are allowed inside. It makes recycling quite easy.

    If you had billions of dollars, would you donate almost all of it to charity? Well, that's what Mark Zuckerburg, CEO and founder of Facebook, just said he would do.
    Zuckerburg and his wife Priscilla Chan promised to give 90% of their Facebook shares to society. Right now that is about $45 billion, and they plan to donate the money to things like science and education.
    Many billionaires have done similar things. Bill Gates, creator of Microsoft, made The Giving Pledge, an activity in which billionaires promise donate more than half of their wealth to charities. This started in 2010, and now 139 people from 15 countries joined it.
    But giving back and helping others isn't just for big billionaires. People like Zuckerberg, and Gates may have more to give, but people with less are doing it, too.
    Especially around the holidays, people want to do their part and give back to people who are less lucky than them. Schools may have food collections where people bring a few food items, and together they can make a big donation to places like homeless people's homes.
    People also host special events like concerts of runs to be creative while raising money. Regular people donate whatever they can to US charities like the United Way and the American Red Cross.
    Then these charities are able to help US communities in different ways like education, health and improving the lives of the poor. These individual donations come together to make a big difference.

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.