题目内容：

    Wind farms have been considered as the way to fight global warming, but a new study suggests they could actually heat the planet up.

The study found that the US would get warmer if the number of turbines(涡轮机）were increased markedly. Researchers say they'll require much more land than previously thought, needing five to 20 times more space than earlier studies have suggested. And winds created by vast fields of turbines could mix warm and cool air, which makes the surface quite warm .

Despite the potential drawbacks, however, the researchers argue wind energy still makes more sense for the environment than fossil fuels. Study coauthor and Harvard University scientist Professor David Keith argued that, when it comes to energy production, there is no free lunch. "Wind beats coal by any environmental measure, but that doesn't mean that its effects can be ignored. We must use fewer fossil fuels to stop carbon production. In doing so, we must make choices between various low-carbon technologies , all of which have some environmental effects , " he said.

More than ten previous studies have now observed local warming caused by US wind farms. Researchers suggested that solar power offers a less damaging energy source in the fight against climate change. In terms of temperature difference per unit of energy generation, solar power has about 10 times less effect than wind, and the solar power energy is mature in a wide range of fields. But there are other considerations. For example, solar farms are dense(密集的）, while the land between wind turbines can be co-used for agriculture.

Tidal power is an environmentally-friendly energy source. In addition to being a renewable energy, it does not give off any climate gases and does not take up a lot of space . However , there are currently very few examples from real tidal power plants and their effects on the environment. Also, it is important to realize that the methods for generating electricity from tidal energy are relatively new technologies. It is projected that tidal power will be commercially profitable within2030 with better technology and larger scales.

1.What is the purpose of the text?

A.To introduce a study finding.

B.To discuss the global warming problem.

C.To prove the benefits of wind farms.

D.To call attention to environmental protection.

2.What is paragraph 2 mainly about ?

A.The effects of global warming.

B.The reason for using wind energy.

C.The disadvantages of wind farms.

D.The working principle of wind farms.

3.What do Professor David Keith's words suggest?

A.Producing energy is easier than before.

B.Consuming energy damages the environment.

C.Burning coal should be totally stopped.

D.Developing low-carbon technologies is hard.

4.Which is recommended considering the environment and practical use?

A.Wind energy. B.Fossil fuel.

C.Tidal power. D.Solar energy.