51. What is the main topic of this passage?
A. The benefits of solar and wind power over conventional energy sources.
B. How energy resources are tapped from nature.
C. Two types of alternative energy sources that should be further utilized.
D. Examples of the use of energy sources worldwide.
52. According to the passage, why should we consider using alternative energy sources?
A. Because fossil fuels are no longer available.
B. Because global warming has increased the amount of sunlight that reaches the earth.
C. Because they are free and available worldwide.
D. Because conventional energy sources are being depleted, and they cause environmental damage.
53. According to the passage, what can be inferred about solar roof tiles?
A. They are being used in many undeveloped countries. B. They can convert geothermal power to electricity.
C. They are more expensive than solar panels. D. They contain photovoltaic cells.
54. According to the passage, how is solar energy production similar to geothermal energy production?
A. They both require fairly simple technology. B. They both use heat from the earth's surface.
C. They both require the use of a generator. D. They are both conventional and costly.
55. According to the passage, which of the following is true about solar power?
A. There is very little of it available in Iceland.
B. There is enough of it to far exceed the energy needs of the world.
C. It is 6,000 times more powerful than energy from fossil fuels.
D. It is being used in 100,000 private homes worldwide.