Parents today also worry about their children's diets. Some doctors give the following advice：

    Are you able to send a letter with pictures and sounds to someone somewhere in the world without a stamp(邮票) on it? Using a computer you can send e-mails quickly and easily. The post is much slower than e-mail. E-mail can send its message to the other side of the world in seconds.

    E-mail is easy to use and it saves time and money. The differences in time in different parts of the world do not matter when sending e-mail. It's twenty-four-hour service(服务) that you can send e-mail at any time of the day or night. No one has to be there to get e-mail. It does not matter if your friends are in beds when you send e-mail to them, or you are seeing a movie at the movie theater when they send e-mail back.

    Now too much CO makes the Earth warmer and warmer, and brings bad effect to people. To save our Earth, a new lifestyle called low-carbon life becomes popular. Low carbon means low energy and no waste. It is necessary for everybody to learn to live a low-carbon life.

    To live a low-carbon life, we'd better save as much energy as we can. For example, turn off the lights and TV when you don't use them, use cold water to wash clothes or dishes: take a short shower and try to take a cold one when the weather gets warm: don't do the cooking with electricity.

    To live a low-carbon life, we should eat less meat. Being a vegetarian can help reduce (v)one and a half ton of carbon dioxide a year, but keeping animals for food produces even more carbon dioxide than all the cars do in the world.

    To live a low-carbon life, we should plant more trees. Trees are very important for us. They can not only produce oxygen for us to breathe and keep the air clean. But also take in the harmful gases from the air. To protect trees we should stop people from cuing down trees and plant as many trees as we can.

    If we can keep them a habit in our daily life, the earth will become a safer planet for us to live on.

    Man has a big brain(脑). He can think, learn and speak. Scientists always say that men are different from animals because they can think and learn. They know now that dogs, rats, birds can learn too. They are beginning to understand that men are different from animals because they can speak. Animals cannot speak. They make noises when they are afraid, or angry or unhappy. Apes(类人猿) can understand some things more quickly than humans. One or two of them can learn a few words. But they cannot join words to make sentences. They cannot think like us because they have no language(语言). They can never think about the future. Language is a wonderful thing. Man can build a modern world because he has language. Every child can speak his own language very well when he is four or five, but no animals learn to speak. How do children learn it? Scientists do not really know. What happens inside our body when we speak? They do not know. They only know that man can speak because he has a brain.