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“Good Greed”Do you want to know how to (1)_____ money and do you bit for the environment? Investing (2)_____ something that will save the planet is becoming easier as the private (3)_____ begins to step in with powerful, profitable-driven for huge world problems. Take energy, for example. More and more investors are now looking to risk huge (4)_____ in alternative energies safe in the knowledge that the world is not safe from carbon emissions.Solar power is one such case. There are a dozen or so (5)_____ traded companies that manufacture solar materials or systems. And some big-name billion-stocks; one producer of high-efficiency solar-power cells, for example, was recently trading (7)_____ the stock market at more than 166 times earnings.Cautious investors can’t forget that a similar optimism was (8)_____ for the peak in e-business stocks in the nineties before the crash. In the case of solar power, such (9)_____ are well-founded because solar energy has one big economic problem: it currently costs roughly twice (10)_____ much per kilowatt- hour as power from the grid.(11) _____, events are changing in a way that may encourage all investors. First, of course, there are rising petroleum prices and on one really believes the cost of natural gas will (12)_____ go down again. Secondly, event as traditional energy prices begin to soar, solar cost are expected to (13)_____ their descent. The cost of a solar kilowatt-hour has declined from 47 cents in 1990 to around 21 cents today, (14)______ it has remained stable. The third force is government subsidies. In the USA, for example, Uncle Sam now gives a 30% tax credit to business that use solar energy --- and that’s just the (15)_____, with much more still to come.123456789101112131415

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试述包与包之间有哪些主要的关系。

简要说明构成包图的基本元素和各自的作用。

选择题( )是用来把元素组织成组的通用机制。

A. 包
B. 类
C. 接口
D. 组件

组成包图的元素有____、____、____。

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