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    Many people today like exercise. Some like to run, and some like to walk. Others dance or play balls. They do different kinds of exercise. Why do people like exercising? It's good for their health. And exercise helps make them tired, so they sleep better at night.

    You may like to run. If you do, take care of your feet. Make sure you have the right shoes. Some people like to run on roads, but they must watch out for cars.

    Walking is a good exercise. You may take a long walk in the park. It's more fun if you don't go alone. Go with a friend. The two of you may have a great time.

    Some people like to swim. But others don't like to go into the water. If you like this kind of exercise, make sure that someone is watching you. You must always take care when you are in the water. Jumping a rope (跳绳) or riding a bike is also good exercise. There are many other exercises. Find out what you like. You may need help at first. Some people often do exercise, and they can help you. Do exercise every day, and you will know what it makes you feel.

每年会出现两次卫星日凌现象，时间分别在 ____  (填节气)前后。