Most cars run on gas. Gas cars work very well. But there is a problem. Cars that run on gas make the air dirty. The dirty air is not good for people, animals or plants. What can we do? We can drive electric cars!

Electric cars do not use gas. These cars do not make the air dirty. They have batteries that power their motors (马达). The batteries can be charged (充电) many times. They can be used again and again. This makes electric cars great. But electric cars have problems too. They are slower than gas cars. They are also very quiet. This means that some people can’t hear them when they go by. They may not think a car coming. So they have to be careful. People are finding ways to make electric cars better all the time. Maybe one day all cars will be electric. That would be much better for the world.

阅读短文，根据短文内容从下面的六个选项中选择五个还原到文中，使短文内容完整、意思连贯。

     Electric cars may seem like a recent invention, but they have been around for years. 【小题1】 At that time, gasoline was expensive compared with other fuels (燃料), so electric cars were more popular.

     When gasoline prices dropped and new technologies on gasoline cars were developed, electric cars were out of date. 【小题2】 During the 20th century, gasoline cars got bigger, heavier and faster. They needed more fuel, and it caused more air pollution. For years, the car makers didn’t worry about pollution. 【小题3】 But when people began to realize that there was not enough oil on the earth, they asked car makers to produce more efficient (高效能的) and less polluting cars.

     One method of solving the problem was a “hybrid” car (混合动力车). 【小题4】 Hybrid cars became popular in the 2000s because gasoline prices went up while prices of hybrid cars went down.

       An all-electric car uses no gasoline. The problem, however, is that car batteries (电池) need to be recharged (再充电). 【小题5】 Many people are not pleased with it. The government and car makers are working together to develop safe, cheap and useful electric cars. When more and more people have these electric cars in the future, a gasoline station may disappear.

China now has more than 30, 000 kilometers of high speed track, and this is expected to increase to 38,000 kilometers by 2025. Fully two thirds of the world’s high speed rail（by length）is in China. Here, we track the exciting technological developments in high speed rail and consider their cultural influence.

While the main advantage of the high speed rail lines is convenience for people to get from one city to another as quickly as possible, some of these high speed lines have become popular tourist attractions（places that many tourists visit）. A good example of this is the Hefei-Fuzhou high speed line. Technically speaking, this was one of the most challenging high speed rail routes ever built; nearly 90% of the track was laid either on bridges or in tunnels（隧道）. However, the amazing views are worth it, as the train goes through some of China’s most beautiful mountainous areas, including the Huangshan and the Wuyi Mountain Ranges.

As China has gained skills and knowledge in high speed rail, it is trying to export（出口）its technology to other countries. Its first project on the international market was the line connecting Istanbul with Turkey’s capital, Ankara, 530 kilometers away. This was followed by projects among other countries. Perhaps its most challenging project is a Trans Asian network（横贯亚洲铁路网）connecting China with Europe. Although it is difficult, China will make every effort to take on this plan. It is hoped to be completed by 2030 as a part of China’s Belt and Road Initiative（一带一路的倡议）.

Thanks to high speed rail, the travel time between main cities in China has already been reduced to only a few hours. So this convenience should improve the development within and out of China. No doubt, it will also bring the people of the country closer together, and in time bring about deep social changes.