The computer in a hybrid car.

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 24 to 30.

Many of the world's cities lie under a permanent blanket of smog. People are concerned about global warming, and fuel prices just keep going up and up. It's no surprise therefore, that in recent years, car manufacturers have been put under pressure to invent a vehicle that is both cheaper to run and better for the environment. Finally, after much trial and error, it seems as though they might be making progress, and the future of the car industry is beginning to look a little "greener".

One of the first ideas which car manufacturers tried was to replace engines which run on fossil fuels with electric motors. Unfortunately, these vehicles had several drawbacks and they didn't sell very well. The problems were that the batteries of these electric cars ran out very quickly and took a long time to recharge. Also, the replacement energy parts were very expensive.

However, the idea of electric cars has not been scrapped altogether. Car manufacturers have improved the concept so that environmentally friendly cars can now be efficient and economical as well. This is where the hybrid car, which has both an electric motor and a traditional petrol engine, comes in. The electric motor never needs to be recharged and it is much better for the planet than a traditional car.

In a hybrid car, the engine is controlled by a computer which determines whether the car runs on petrol, electricity, or both. When the car needs maximum power, for example, if it is accelerating or climbing a steep hill, it uses all of its resources, whereas at steady speeds it runs only on petrol. When slowing down or braking, the electric motor recharges its batteries.

Hybrid cars are better for the environment because the electric motor can help out whenever it is needed and they have a much smaller engine than a traditional car. Also, hybrid cars on the market are made using materials such as aluminium and carbon fibre, which makes them extremely light. Both of these factors mean that they use far less petrol than normal cars, so they produce less pollution.

Of course, hybrid cars aren't perfect; they still run on fossil fuel and so pollute the environment to some extent. However, they may be the first step along the road to cleaner, "greener" cars. Car manufacturers are already working on vehicles which run on hydrogen. The only emission from these cars is harmless water vapor. These are still some way in the future, though, as designers need to think of cheap and safe ways of producing, transporting and storing hydrogen, but at last, it looks like we might be heading in the right direction.