Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A,B,C and D.You should decide on the best choice and mark the corresponding letter on Answer Sheet 2 with a single line through the centre.Passage OneQuestions 1 to 5 are based on the following passage. Almost 150 years after photovoltaic(光电的) cells and wind turbines(涡轮机) were invented，they still generate only 7% of the world's electricity. Yet something remarkable is happening. From being secondary to the energy system just over a decade ago, they are now growing faster than any other energy source and their falling costs are making them competitive with fossil fuels. BP, an oil firm, expects renewables to account for half of the growth in global energy supply over the next 20 years. It is no longer far-fetched to think that the world is entering an era of clean,unlimited and cheap power. There is a problem， though.To get from here to there requires huge amounts of investment over the next few decades. Normally investors like putting their money into electricity because it offers reliable returns. Yet green energy has a dirty secret. The more it is used,the more it lowers the price of power from any source. That makes it hard to manage the transition to a carbon-free future,during which many generating technologies，clean and dirty,need to remain profitable if the lights are to stay on.Unless the market is fixed，subsidies to the industry will only grow. Policymakers are already seeing this inconvenient truth as a reason to put the brakes on renewable energy. In parts of Europe, investment in renewables is slowing as subsidies are cut back. However, the solution is not less wind and solar. It is to rethink how the world prices clean energy in order to make better use of it. At its heart,the problem is that government-supported renewable energy has been imposed on a market designed in a different era. For much of the 20th century，electricity was made and moved by vertically integrated， state-controlled monopolies. From the 1980s onwards,many of these were broken up, privatized and liberalized, so that market forces could determine where best to invest,Today only about 6% of electricity users get their power from monopolies. Yet everywhere the pressure to decarbonize power supply has brought the state creeping back into markets. This is disruptive for three reasons. The first is the subsidy system itself. The other two are inherent to the nature of wind and solar; their intermittency and their very low running costs. All three help explain why power prices are low and public subsidies are addictive.1. Why can photovoltaic cells and wind turbines compete with fossil fuels?A. They are clean and unlimited.B. Their costs keep lowering down.C. They can produce power more efficiently.D. They receive more subsidies from the government.2. What is the dirty secret of green energy?A. Its equipment requires frequent maintenance.B.It offers little reliable returns to the investors.C. It costs a lot to transport the electricity it produces.D. Its use will reduce the price of power.3. Why are policymakers unwilling to develop renewable energy?A. It needs a large amount of subsidies from the government.B. It is inconvenient to manufacture wind turbines and solar cells.C. Green energy will bring negative influence on coal power plants.D. The government needs to subsidize many other public services.4. What can be done to make better use of green energy?A.To update generating technologies of green energy.B. To bring more private enterprises into the market.C To set a reasonable price on clean energy.D. To increase subsidies to green energy.5. What is the problem with renewable energy in nature?A. The market is designed in different times.B. Monopolies still supply most of green power.C.Market forces couldn't determine where to invest.D Companies in this field can't remain profitable.