单项选择题The Solar Decathlon is under way, and teams of students from 14 colleges and universities are building solar-powered homes on the National Mall in Washington, D. C. in an effort to promote this alternative energy source. This week judges in this Department of Energy (DOE) sponsored event will evaluate these homes and declare one the winner. Unfortunately, for the participants, it rained on the Sept 26th opening ceremonies, and the skies over the Washington have remained mostly overcast since. However, the conditions may have made for a more revealing demonstration of solar energy than was originally planned.Although the Solar Decathlon's purpose is to advertise the benefits of electricity-generating solar panels and other residential solar gadgets, the bad weather has made it hard to ignore the limitations. As fate so amply demonstrated, not every day is a sunny day, and indeed DOE's 'Solar Village on the National Mall' has received very little of what it needs to run.Since solar is not an always available energy source, even a community consisting entirely of solar homes and businesses would still need to be connected to a constantly-running power plant (most likely natural gas or coal fired) to provide reliable electricity. For this reason, the fossil fuel savings and environmental benefits of solar are considerably smaller than many proponents suggest.Washington, D. C. gets its share of sunny days as well, but even so, solar equipment provides only a modest amount of energy in relation to its cost. In fact, a $ 5, 000 rooftop photovoltaic system typically generates no more than $100 of electricity per year, providing a rate of return comparable to a passbook savings account.Nor do the costs end when the system is installed, lake anything exposed to the elements, solar equipment is subject to wear and storm damage, and may need ongoing maintenance and repairs. In addition, the materials that turn sunlight into electricity degrade over time. Thus, solar panels will eventually need to be replaced, most likely before the investment has fully paid itself off in the form. of reduced utility bills.Solar energy has always had its share of true believers willing to pay extra to feel good about their homes and themselves. But for homeowners who view it as an investment, it is not a good one. The economic realities are rarely acknowledged by the government officials and solar equipment manufacturers involved in the Solar Decathlon and similarly one-sided promotions. By failing to be objective, the pro-solar crowd does consumers a real disservice.The Solar Decathlon is most probably the name of a ______.
A．technology
B．contest
C．strategy
D．machine
