With the world's population estimated to grow from six to nine billion by 2050, researchers. businesses and governments are already dealing with the impact this increase will have on everything from food and water to infrastructure (基礎(chǔ)設(shè)施) and jobs. Underling all this __1__ will be the demand for energy, which is expected to double over the next 40 years.

Finding the resources to meet this demand in a __2__. sustainable way is the cornerstone (基石) of our nation's energy security, and will be one of the major __3__ of the 21st century. Alternative forms of energy- bio-fuels, wind and solar, to name a few are __4__ being funded and developed, and will play a growing __5__ in the world's energy supply. But experts say that even when __6__, alternative energy sources will likely meet only about 30% of the world's energy needs by 2050.

For example, even with __7__ investments, such as the $93 million for wind energy development __8__ in the American Recovery and Reinvestment Act, important alternative energy sources such as wind and bio-fuels __9__ only about 1% of the market today.

Energy and sustainability experts say the answer to our future energy needs will likely come from a lot of __10__ both traditional and alternative.

[A] stable

[B] solutions

[C] significant

[D] role

[E] progress

[F] marvelous

[G] included

[H]growth

[I] exactly

[J] consist

[K] comprise

[L] competitions

[M] combined

[N] challenges

[O] certainly

答案解析：

1 growth 2 stable 3 challenges 4 certainly 5 role 6 combined 7 significant 8 included 9 comprise 10 solutions

【解析】這是一篇討論能源資源的說明文，話題是考生比較熟悉的能源問題，不斷增長的人口與可再生資源的矛盾該如何解決。文中指出能源的一些可替代形式 如生物能源、風(fēng)能太陽能等可再生資源將在未來發(fā)揮越來越重要的作用。但是專家指出，即使這些資源儲備量驚人，但是到2050年也只能滿足世界30%的需求。文章最后兩段探討了各能源在市場上的需求，以及解決未來能源需求的其他方案。

總體來說，這篇文章理解難度不大，填空難度適中，所選詞匯也都是四級考綱的詞匯。選項較具有干擾項，多為c和s開頭的單詞，考生在考試時要特別注意。