All energy sources have their pros and cons—their good points and bad points. Modern societies have to make many decisions about how best to produce energy. The needs of the society have to be balanced against the need to protect the environment.

Fossil fuels—coal, oil and natural gas—are a leading energy source around the world. They are called fossil fuels because they were formed from the remains of plants and animals that died many millions of years ago. Since then, great heat and pressure (压力) deep in the ground have changed them. So the fossil fuels we use today are found underground.

One of the main advantages of fossil fuels is that they are abundant—found in many places and in large amounts. In addition, they contain a lot of usable energy. Coal is especially abundant. A special advantage of natural gas is that it burns very cleanly. When natural gas burns, it produces mostly carbon dioxide and water vapor. Oil’s main advantage is that it burns efficiently—meaning that little is wasted in the change to energy. Also, the refining (提炼) process that makes gasoline (汽油) and diesel produces other petroleum products, which are used in crayons, bubble gum, eye glasses, and even artificial heart valves.

All fossil fuels are basically non-renewable (不可再生的) because nature cannot create enough to keep up with demand. Many experts think that the world’s oil wells will be empty in a few decades (十年). But, even before then, the oil supply will be too small to meet global demands. Also, fossil fuels produce pollutants. Cars, factories, and many power plants release harmful chemicals into the air. As long as fossil fuels are burned, air pollution will continue to be a problem.

Another problem is the greenhouse effect. Gases released from burning fossil fuels trap (储存) more heat in Earth’s atmosphere than would be trapped naturally. This heating up of Earth’s atmosphere is called global warming. Scientists think carbon dioxide contributes most to worsening the greenhouse effect, so even natural gas adds to the problem.

We need energy, and the fossil fuels that supply most of our energy will not last forever. Finding renewable alternatives (替代品) is key to the world’s energy future. Scientists will continue to do research. Each new source of energy will have its pros and cons, too. Governments and environmentalists will continue to debate which energy sources are the best while our need for energy continues to grow.

【推荐2】People try to make predictions about the future. But what surprises does technology have in store for us? The answer is nanotechnology (纳米技术).

Nanotechnology is the science of building tiny machines, so small that they are invisible. To give you an idea of the size of these machines, the difference between a nanometer and a meter two units of length, is the same as the difference between a rock and the planet Earth! Most scientists agree that nanotechnology will change our lives in the future—but how? At the moment it’s difficult to predict whether this new technology will be like a wonderful dream, or a terrifying nightmare (噩梦).

In the 1966 the film Fantastic Voyage, an inventor develops an amazing new way to treat diseases. He narrows a group of scientists and their machines and injects (注射) them all into a patient. They then travel around the patient’s body, visiting the different parts of the body and repairing them. Of course, this is just a film—but the reality of nanotechnology is not very different. Scientists are already making nanobots, tiny robots that are very small. In the future, doctors might be able to inject these into a patient, and the nanobots will travel around the body and repair the diseased parts.

Some people are worried that nanotechnology could be difficult to control. Nanobots might come into the environment and damage people, plants and animals. Others have even more serious worries. Eric Drexler is a futurist, a scientist who makes predictions about the future. In his book Engines of Creation he predicted the invention of nanobots. He also described a special kind of nanobot that can make a copy of itself using the materials around it—and this is where the nightmare begins. In Michael Crichton’s book Prey, nanobots reproduce themselves so quickly that they use all the materials around them and then look for more and more, and more, eventually “eating” the world. Some people are worried that this might really happen. The most serious predictions (that very few scientists believe) say that nanobots could destroy the whole planet in about three hours!

Last week we went on a school trip to a science museum. Ms. Liu, the guide, showed us around a smart home.

We started with the front door. Ms. Liu asked me to ring the doorbell. I didn’t notice the tiny camera that was fixed just above it. After I pressed (按) the doorbell, the camera sent a live video (视频直播) to the home-owners. “They can electronically open the door when they are not at home,” said Ms. Liu.

The other thing I couldn’t see on the door was a lock. “There must be one,” I thought. At this time, Ms. Liu took out a smart phone and put it against the door. And it opened. “Oh, the key is on the smart phone.”

After entering the living room, I saw a computer on a table. By using the computer, the owners can control how much energy is used. In this way, they can manage their living cost.

One of the rooms I wanted to see most was the bedroom. To my great surprise, the bed disappeared into the floor at the touch of the smart phone. The window has a smart blind (百叶窗). It can be raised and lowered with a voice.

As I left the smart home, I looked back on what I had just seen. Scientists often say that these products are improving our life. I think the technology in the smart home may make us lazier. However, there is no doubt that it will become more popular in the homes of tomorrow.

1、2题完成句子；3~5题简略回答问题。

English is like every other things. If the student doesn’t actually take action in learning the language, then, it is useless for him or her to learn it at all.

In fact, there are few who actually master the language. And there are many who hate learning it. But students are required to learn English. Scores are the most important thing for them if they want to enter a good senior high school and college. But for those who want to study abroad, things are different. They need to have exams, for example, the TOEFL exam, that require a higher level of English than just studying for the zhongkao or gaokao exams. They also need to be able to listen to a professor who teaches them without any translation into Chinese.

The main language of educational, scientific, cultural and academic (学术的) exchanges around the world is English. So if you have a dream of studying or working abroad, then, you need to take steps to master English now. If you only want a high score for gaokao, then, you still need to at least achieve the goal of getting the high score.

When you know why you want to learn English, then, you can take steps in finding out how to achieve what you want. And remember “Knowing is not enough; we must apply. Willing is not enough; we must do.”