【单选题】

In technologically advanced societies, the enormous consumption of energy per head is one aspect of the ever-increasing pressure man is placing on his environment.Early industrial man used three times as much energy as his agricultural ancestor; modern man is using three times as much as his industrial ancestor. If present trends continue, the rate of consumption will have tripled (3倍) again by the end of the century. The problem lies in the fact that most of our current energy sources are finite. The hard truth is that a day will come when there is little or no exploitable coal, oil or natural gas anywhere. The sharp rise in the price of oil over the last decade has been unpleasant for many parts of the world but in the long run it is beneficial, partly because it discourages waste and partly because it has forced many nations to seek ways of developing better and more permanent sources of energy. Energy sources may initially be divided into two kinds: nonrenewable (i.e. finite) and renewable. The former group includes coal, oil, and gas, in the long run, nuclear; the latter hydro-powers, solar power and wind power. The energy from all these sources ultimately derives from the sun. There is a further source — geothermal— which depends on the earth’’s own heal. In practice this may be classed as nonrenewable as it is exploitable in only a few places and even that is limiteD、There is a second distinction that is often made between conventional and non-conventional energy sources.

A、conventional energy source is one which is at present widely exploiteD、In view of the points made in paragraph 1 (above) it will be realized that, broadly, the conventional sources are the non-renewable ones. This is not entirely true, however, as a good deal of oil is locked up in solid form in rock (tar sands and oil shale) and this source, though non-renewable, is also non-conventional, since it has not so far been developed very much. We are warned that__________.
A、the renewable energy source will be less and less
B．the non-renewable energy will be more and more
C．there will be no energy source
D．heat energy will be permanent