How do you study each day? You may answer it in one second: have classes at school, take notes and do homework. Feeling a little bored? There are other ways that can make learning interesting and varied. It's called digital learning.

    Digital learning is a way to help students learn by using the Internet. There are three important kinds of digital learning. Apps are computer software applications (应用). People can download them on their mobiles. The other two kinds are social networking services, including weibo and WeChat and websites. Every one of them is like your teacher. They help you master what you learn at school.

    Compared with traditional learning ways, digital learning has its advantages. Digital learning is also varied. It covers almost every school subject. More importantly, it always offers students the newest resources (资源) to learn from.

    Digital learning is also personalized. You can choose what you like to learn. If you don't master what you have learned at school, you can learn again through digital ways.

    However, digital learning also has disadvantages. When you use digital ways to learn, you've got little chance of talking with teachers and classmates. As digital learning uses computers or smartphones, watching the screen too long may be bad for your eyes. It is better to take a rest every 20 minutes.

    Butterflies are common all over the world，but butterflies in hotter countries are usually bigger and more brightly colored than those in cooler countries，and there are more different kinds．

   Usually the male butterflies are more brightly colored than the females．The females have bigger and heavier bodies since they carry the eggs．The bright colors of the males help to attract the females，and the duller colors of the females make them less likely to be caught by enemies before they have laid their eggs．

   Some butterflies have bright pattern colors on the upper surface of their wings that show when flying ,but when they rest on a tree or leaves , they close their wings．On the undersides of their wings there are green and brown marks which look like the tree or leaves．They are then difficult to be seen．The best example of this is the Dead Leaf Butterfly．When its wings are c1osed，it looks exactly like a dead leaf．There are even marks that look like the holes in a dead leaf．When the butterfly is run after by a bird，it closes its wings and seems to have disappeared completely．

Under the beauty of their colorful covers, the butterflies have their own way to avoid being killed by their enemies. So do the other animals. That's the rules of the nature and also the gifts that were born with.Many butterflies have round marks on their wings that look like eyes.The round marks have a useful function(功能)．When the butterflies are resting，their wings are closed，and these marks can't be seen. When a bird sees one，and begins to attack it，the butterfly will open its Wings. The bird thinks that it sees two eyes staring at it，frightened，and flies away.

    Life in the future will be different from life today. Between then and now many changes will happen. But what will the changes be?

    The population is growing fast. There will be many people in the world and most of them will live longer than people live now.

    Computers will be much smaller and more useful, and there will be at least one in every room. And computer studies will be one of the most important subjects in schools then. People will work fewer hours than they do now and they will have more free time for sports, watching TV and travels. Travelling will be much cheaper and easier. And many more people will go to other countries for holidays.

    There will be changes in our food too. More land will be used for building new towns and houses for all the people. Then there will be less room for cows and sheep, so meat will be more expensive. Maybe no one will eat it every day. Instead they will eat more fruit and vegetables. Maybe people will be healthier. Work in the future will be different too. Robots will do dangerous and hard work. Because of this, many people will not have enough work to do. This will be a problem.

    In earliest times, men considered lightning to be one of the great mysteries (神秘的事物) of nature. Some ancient peoples believed that lightning and thunder were the weapons (武器) of the gods.

    In reality, lightning is a flow of electricity formed high above the earth. A single flash of lightning 1.6 kilometres long has enough electricity to light one million light bulbs (灯泡).

    The American scientist and statesman, Benjamin Franklin, was the first to show the connection between electricity and lightning in 1752. In the same year he also built the first lightning rod (避雷针). This device (装置物) protects buildings from being damaged by lightning.

    Modern science has discovered that one stroke (闪击) of lightning has a voltage (电压) of more than 15 million volts (伏特). A flash of lightning between a cloud and the earth may be as long as 13 kilometers, and travel at a speed of 30 million meters per second.

    Scientists judge that there are about 2,000 million flashes of lightning per year. Lightning hits the Empire State Building in New York City 30 to 48 times a year. In the United States alone it kills an average (平均数) of one person every day.

    The safest place to be in case of an electrical storm is in a closed car. Outside, one should go to low ground and not get under trees. Also, one should stay out of water and away from metal fences. Inside a house, people should avoid open doorways and windows and not touch wires or metal things.

    With lightning, it is better to be safe than sorry?

    The Earth is about 4, 600 million years old Man lives on the Earth for only 35, 000 years. But we change our Earth in many ways. Many things we do are good, but some are not good for the Earth.

    Water pollution

    A lot of people, birds and fish die each day because of water pollution. Factories pollute the water. As a result (因此), the water in many rivers and lakes is now very dirty.

    Air pollution

    In big cities, factories, cars and buses are the main causes of air pollution. Many people in cities now have health problems. For example, Mexico City used to be a beautiful sunny capital, but today there are many clouds in the sky. And many people get ill because of the polluted air.

    Soil (土壤) pollution

    In order to have a better harvest (收获), some of the farmers use chemicals too much in their fields. That's bad for the soil.

    Hope for the future

    These problems are very serious for our future, so all of us should do something to protect the environment. If we can stop pollution, our Earth will become more and more beautiful.