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 ugly teeth. For example, one of my classmates, Mile, doesn't have very nice teeth,so thatis why he seldom opens his mouth.he even says that he has lost cofidence 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 teeth problems from their parents,while others'teeth are damaged because of bad habits,like heavy smoking,eating too much sugar or not brush-ing 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 then.
   Smiling can help you to feel more confident and make other people think of you as a more friendly person. If you want to keephealthy, you should not only smile but also laugh. An Indian doctor called Kataria said that young children should laugh about 300 times a day, wile adults should laugh between 7 and 15 times a day. So please take this chance to smile and laugh now!

    What's the first thing that you notice when you walk into your favorite restaurant? Is it the smell of fresh pizza, or the sight of your favorite desserts? Food that looks and smells good will probably taste good, but what about sound? Is that important, too?

    Scientists now believe that the taste of food can change when your ears hear different sounds, but it has to be right kind of sound. When you turn on a microwave with popcorn in it, it soon starts to pop. Do you think, "That sounds tasty!"?Not really, you probably think it's nearly ready. But when you smell it, you go to get the salt and the butter. Hearing the popcorn makes you think about it, but smelling it tells you that it tastes good. So what arc the sounds to change the tastes of the things?

    In an experiment(实验)in a fish restaurant, customers(顾客)listened to the sound of the seaside while they ate. Did it make a difference? Yes, it did Listening to the sea seemed to improve the taste of the food. It was fresher and saltier. When the restaurant tried the same experiment with the sound of the farm animals, there was no difference in taste. The results are going to be useful for restaurants. Perhaps they will try to use fewer unhealthy things, like salt and sugar in food With the right music or sounds, perhaps we won't taste the difference.

    Restaurants are also beginning to set a connection(联系)between food and the sound that the packet(包装袋)makes. Pick up a packet of your favorite potato chips, what does it sound like? One restaurant recently changed the material(材料)that they used to make their potato chip packets because experiments show that the packet which makes a right noise will make customers think the potato chips are fresher. Another idea is that a list of music will begin to appear on food packets, so if you don't like your green vegetables, the right music or sounds could help you learn to love them.

    Scientists in Britain and the United States have made a new kind of enzyme(酵素) that eats plastics (塑料). With its help, plastics can be turned into smaller parts and go away quickly. Scientists believe that, in the future, it could solve the problem of plastic pollution.

    The enzyme is able to break down PET, a form of plastic. PET was first made in the 1940s and is now widely used to make plastic bottles. It can remain in the environment for many years and pollute large areas of land and water. So it has always been a headache to deal with the waste from PET and other plastics.

    The researchers made the discovery (发现) while examining the structure of a natural enzyme in Japan. They found that the natural enzyme was helping to break down PET plastics. So, they decided to make small changes to the enzyme by adding some amino acids (氨基酸). It made the natural enzyme's plastic-eating abilities work faster and better.

    John McGeehan, one of the lead researchers, said, "We've made an improved enzyme. It's better than the natural one. And we are trying to make more improvements to it." He went on, "The enzyme is not harmful to humans or animals, and it is friendly to the environment. So we are considering putting it into wider use."

    The team is now trying to make the enzyme break down PET in large quantities (大量地).

    "We'll see that the plastic pollution may be stopped with this technology. However, there is still a long way to go," John McGeehan added.