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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 (基础设施) and jobs. Underling all this 47 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 48 . sustainable way is the cornerstone (基石) of our nation's energy security, and will be one of the major 49 of the 21st century. Alternative forms of energy- bio-fuels, wind and solar, to name a few are 50 being funded and developed, and will play a growing 51 in the world's energy supply. But experts say that even when 52 , alternative energy sources will likely meet only about 30% of the world's energy needs by 2050.
For example, even with 53 investments, such as the $93 million for wind energy development 54 in the American Recovery and Reinvestment Act, important alternative energy sources such as wind and bio-fuels 55 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 56 both traditional and alternative.
What determines the kind of person you are? What factors make you more or less bold,intelligent, or able to read a map? All of these are influenced by the interaction of yourgenes and the environment in which you were 47 . The study of how genes andenvironment interact to influence 48 activity is known as behavioral genetics. Behavioralgenetics has made important 49 to the biological revolution, providing information about theextent to which biology influences mind, brain and behavior.
Any research that suggests that 50 to perform certain behaviors are based in biology iscontroversial. Who wants to be told that there are limitations to what you can 51 based onsomething that is beyond your control, such as your genes? It is easy to accept that genescontrol physical characteristics such as sex, race and eye color. But can genes alsodetermine whether people will get divorced, how 52 they are, or what career they are likely tochoose? A concern of psychological scientists is the 53 to which all of these characteristicsare influenced by nature and nurture(养育), by genetic makeup and the environment.Increasingly, science 54 that genes lay the groundwork for many human traits. From thisperspective, people are born 55 like undeveloped photographs: The image is already captured,but the way it 56 appears can vary based on the development process. However, the basicpicture is there from the beginning.
47. M) raised
48. L) psychological
49. E) contributions
50. A) abilities
51. B) achieve
52. N) smart
53. I) extent
54. J) indicates
55. G) essentially
56. H) eventually