[单项选择]Interest is steadily spreading from a minority of enthusiasts in developing renewable sources of energy--wind, wave and solar power, tidal and geothermal energy. Additional support for them has come with a proposal to explore the untapped sources of hydroelectric power in Scotland. The details are presented by Mr. William Manser in a study called "The Case for an Inquiry into Hydroelectric Generation in the North of Scotland". He calls for an expert committee to look at the developments possible for hydroelectric sites and, more important, for means of financing them There is a clear industrial connection in Mr. Manser’s study because it was done for the Federation of Civil Engineering Contractors; hydroelectric schemes, by definition, have a large civil engineering component in them. Mr. Manser estimates that wind power could theoretically provide more than 7 percent of electricity supply in the United Kingdom if suitable sites for generators could be found. However, the pra A. reduce water pollution or smoke creation B. preserve the natural beauty of the area C. make the dam more impressive in itself D. save running cost as much as possible