【正文】 r way is to take the place of the car engine by something. Now inventors are working on steam cars as well as electric cars. Many makers believe that it will take years to develop a useful model that pleases men.To prevent the world from being polluted by cars, we make some changes in the way many of us live. Americans, for example, have to reduce the number of their total cars. They are encouraged to travel and to work by bicycle. It is thought to help man to keep the air clean.But this change does not e easily. A large number of workers might find themselves without jobs if a car factory closed. Thus the problem of air pollution would bee less important than that of unemployment.Although cars have led us to better life, they have also brought us new problems.Time Is Money“Time is money.” This saying means that time is very valuable.But time is more valuable than money. The money we have lost can be gained again, but the time we have wasted cannot be regained. Moreover, sometimes persons can exist without money, but nothing can be done without time, just as no one can live without air.Despite being so valuable, time is often neglected by men. Since time is an invisible thing, men often waste their time unconsciously（無意地）. Without anything to do, they may gossip from morning till night.Man can live only at most to about 100 years. It seems fairly long, but in fact it is rather short. We often say “How quickly time flies!” How many things can a man acplish in such a short period? Hence we should use the valuable time properly to do our work. We will race with it. We will study and work hard. Never waste a little bit of it.Try to Be a Good StudentPerhaps it is the dream of everyone to be a good student at school, but quite a few students feel at a loss on how to make it. In my opinion it is rather easy if you can act on the following points.First of all, make full use of your time and work hard. Don’t put off till tomorrow what should be done today, as time past will never e back. The fast developing society requires adequate knowledge, which presses us to spare no efforts to study. Of course, your hard work will be rewarded one day.Secondly, use your own head and present your point of view. Credulous（輕信的）attitude will only make you take anything for granted. With your own judgment you will be able to tell right from wrong and set up your own theory.Thirdly, set aside enough time for relaxation, entertainment, etc. don’t ignore the harm of all work and no play. Proper sports will build up your body and improve the efficiency of your studying. To be a good student is easier said than done, for it needs a student’s consistent efforts. But nothing is difficult to a man if he puts his heart into it.Natural ResourcesNature has provided us with many kinds of resources. Almost everything we use in our everyday life es from Nature. The food we eat, the water we drink, the clothes we wear, the concrete and bricks to build our houses, the materials to make bikes we ride, etc. all e originally from Nature.People have been making use of these natural supplies for thousands of years. With the development of technology and the increase of the population, the amount and range of materials taken has increased. It is estimated that this tread will continue in the years to e.However, natural resources are not in exhaustible. Some resources are already nearly used up. For example, the end of the world’s fuel is already within sight. Such an essential daily item as water is in short supply in many parts of the world. We can no longer thoughtlessly use the many resources provided by Nature. We must learn to conserve what remains.We Have Only One WorldWhen industries grow, pollution also grows. Today the problem of environment has bee more and more important. The world population is rising so quickly that the world has bee too crowded. We are using up our natural resources too quickly and at the same time we are polluting our environment with dangerous chemicals. If we don’t take action immediately, then we will destroy our only world.Man has made great progress in environment protection. Government of many countries has established laws to protect the forest and sea resource and to stop the environmental pollution.Still more measures should be taken to solve the problem. First, we should start by educating the public about the hazards of pollution. The government on its part should also design stricter laws. This is not only for our own generation but also for the future generation to e.It is necessary to protect our nature environment. We must begin now to protect our only world.Make The Best Use of Our LandIt is the land that has been providing us with everything we need for centuries. In other words, almost everything we use daily es from the land directly or indirectly. The food, clothes, houses, even the books and furniture are all supplied by the land. But the limited land is decreasing at a surprising speed. With the expanding of the cities, the development of the industry and over population, lots of large pieces of good farmland are being turned into residential areas with many houses and apartment buildings, or industrial areas, or warehouses.Therefore some measures must be taken to stop the abusing of our farmland. On the other hand, we should let everyone realize the danger of being short of land. And also we should educate them how to make better use of our land.HealthIt is said that we do not properly value a thing until we have lost it. It is only when a friend dies that we find out how much he was to us. So it is with health. When we are young and strong and have good health, we think little about it. It seems natural to us to be always well, and we cannot imagine what it is like to be ill. Wo we are often careless about our health, and without thinking we spoil our health by bad habits and doing silly things. It is only when we have our good health that we find that it was one of God’s best gifts to us.Health is our most important possession. We should do our best to maintain it. Good health is necessary to happiness and success. People who are in poor health are often pessimisti