A smile will tell people around you that you are a kind and friendly person. However, many people don't smile because they think they have ugly teeth. For example, one of my classmates, Mike, doesn't have very nice teeth, so that is why he seldom opens his mouth. He even says that he has lost confidence because of his teeth. So it is very important for us to look after our teeth. In fact, a lot of people have this problem. Some people inherit tooth problems from their parents, while others' teeth are damaged because of bad habits, like heavy smoking, eating too much sugar or not brushing teeth often. If your teeth are in bad shape, you should see a dentist and ask for help. They can help improve your teeth and tell you how to take care of them.

    Smiling can help you feel more confident and make people think of you as a more friendly person. If you want to keep healthy, you should not only smile but also laugh. An Indian doctor called Kataria said that young children should laugh about 30 times a day, while adults should laugh between 7 and 15 times a day. So please take this chance to smile and laugh now.

注意：①每处错误及其修改均仅限一词；

②只允许修改10处，多者（从第11处起）不计分。

    Last month, my classmate, John, caught bad cold. The news which he was running a high fever and ordinary medicine hadn't worked on him immediate reached everybody in our class. Some recorded the English lessons for him so that he could keep up on his studies. Our English teacher calls on him at weekends. Thanks to everybody's kind help, he failed to falling behind in his studies and finally came back to the class. With love, no illness or difficulty are terrible. Love and help are two-way streets. Our classmates were offered John help partly because he had always been a warm-heart boy. So I realise that when we help others, we are helping us.

    I was asked by a reader recently why so many animals seem to have pink ears, when their bodies are all different colours? The truth is that most animals actually don't have pink ears. Let us explain.

    Near the equator (赤道), where the climate is hot, animals are likely to have darker skin, including on their ears. Think of the African elephant, which has quite dark ears. In colder climates, skin colour is usually lighter and often pink.

    Why is skin colour different in different climates？Skin pigmentation, which is what gives skin its colour, can protect against sunburn and skin cancer (癌症). When animals live in colder parts of the world, they don't need it as much to survive. Light-coloured skin also helps animals stay warmer because it reduces heat loss, which is useful if you're in a colder climate.

    For most animals, the colour of their fur or other body covering has generally developed as camouflage. That allows animals to mix into the background and avoid being eaten, or for predators (捕食者) to remain hidden during hunting. One example is the sandy-coloured coat of the desert fennec fox, which uses camouflage for both hunting and hiding.

    By the way, in many animals, ears come in many different shapes and sizes. For example, in bats, the serval (a type of African wildcat) and the fennec fox, the ears are large compared to their body size—this helps them hear better because it allows them to sense more sound waves. Naked mole-rats have tiny ears because they need to dig a lot. Big ears would get in the way. The other downside of big ears is that you can lose a lot of body heat. That's why animals that live in really cold places, like the Arctic fox, have quite small ears.