Have you ever seen a horse with toes? Millions of years ago, horses had many toes. They had four toes on each front foot. They had three toes on each back foot. The horses were no bigger than cats.

    These small horses lived in the forest. Their many toes helped the horses run over the soft, wet ground.

    It was very hot in the forest. But the weather changed. It became cold. Many trees could not live in cold weather. The trees died and fell. Open fields took the place of forests. The sun made ground dry and hard.

    Horses began to change, too. They began to get bigger. This took a long time. On the dry, hard land, horses needed only their middle toes for running. Their middle toes became hard. After a long while, horses had only one hard toe on each foot. We call this hard toe a hoof.

    Many people today like reading stories about UFO.Many people in different countries are studying the UFO.

    There are some different saying for UFO.Among those sayings,the most popular one for UFO is that UFOs are strange creatures(生物) to the earth from other stars.We can call them aliens.

    UFO scientists and many people believed this saying.Some people said that they saw a few UFOs landing on the earth.They seemed to be objects rather like big plates.Some people said that they saw some strange visitors coming out of the UFOs.

    Some people make mistakes when they say they have seen UFOs high in the sky.Perhaps they see a weather balloon or an uncommon plane or the light they see in the sky comes from the ground.Sometimes they see the light from the moon.

    But these are a lot of others we can't understand.It may take many years to find a clear answer and then people will give UFO another name.

    The human brain weighs about 1.4 kilograms, but it can hold much more information than most computers．However, there is another difference between humans and computers．Computers don't forget information they are given, but humans often do．No one remembers everything, and luckily we don't usually have to．But everyone can improve their memory if they want to．Here are some suggestions．

    Try to use new information immediately．For example, if you meet someone who says "Hi! I'm Carlos．"Don't just say "Hello．" Repeat the person's name．Say "________"

    Break a big number into smaller parts． For example, it's hard to memorize (记忆) 109244153．But if you break it into three parts  109/244/153--it becomes easier．

    Write out what you need to remember over and over again．This will help you keep it in mind longer, especially for memorizing formulas (公式) or facts．

Always review information．If you bring what you've learned back to your mind, it becomes easier to remember． For example, before you go to sleep, it's a good idea to review the new things you learned that day．

    Discuss with a friend．It is always easier to remember things through discussions．You can have a discussion about what's right and what's wrong, and it will lead to the right answer．

    Never tell yourself that you have a bad memory．You can always do something to help improve your memory．And everyone's memory gets better if they use it often enough．

    All the suggestions are helpful．If you follow them, you are certain to improve your memory．

    It is important for us to look after the Earth well. The Earth gives us a lot of things. We also give the Earth a lot, but some of the things are not good.

    In nature, when something dies, other animals and plants get food from it. Every animal or plant provides food for other animals or plants. However, animals can't get food from many of the things that we"give" the Earth. Animals and plants can't cat metal, plastic or glass. These things will stay in the ground for many, many, many years.

    Some rubbish is very dangerous for plants and animals. In some places, many animals live together. One animal makes food for many other animals. If we throw rubbish and chemicals into the water, the plankton（浮游生物）can die. If there isn't any plankton, many animals have nothing to eat.

    So what can we do? Don't leave any rubbish in the countryside! Don't make so much rubbish.

    Now, it seems that artificial intelligence(人工智能) is becoming more and more popular in our life, and it has greatly influenced the ways we live, work and play. Can you imagine that you can play table tennis with a robot one day?

    Recently, a scientist has invented a special robot that can be a table tennis coach. That means people can practice table tennis not only with humans but also with a robot.

    Named Forpheus, the smart table tennis robot is quite special. It can study the movements of human players and the speeds of the ball. In this way, it can exactly judge(判断) the players' skill levels(水平).Then it uses the information to change the ways to play. If the players are just beginners, Forpheus will play in a slow and easy way, but if the players are better ones, the robot will play in a faster and more difficult way. What's more，while playing, it encourages players 10 try their best with words like "Good job!" "Come on!" and so on. At the same time, it gives some good advice to improve their sill so it is a good partner and clever coach.

    Science and technology is developing quickly these days and it's hard to imagine what will happen in the future." In the next 20 years, it will be possible that one robot teaches another to play table tennis or even invents another one!" Takuoya, the inventor of the robot, said.