Energy sources may initially be divided into two kinds: non-renewable and renewable. The former group includes coal, oil, gas and, in the long run, nuclear; the latter waterpower, solar power and wind power. The energy from all these sources ultimately derives from the sun. There is a further source 一 geothermal 一 which depends on the earth’s own heart In practice this may be classed as non-renewable as it is exploitable in only a few places and is limited. There is a second difference that is often made, between traditional and non-traditional energy sources. A traditional energy source is one which is at present widely exploited. It will be realized, broadly, that the traditional 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 and this source, though not renewable, is also non-traditional, since it has not so far been developed very much.

Shopping On Line

take into account

draw on

run for

be compatible with

in advance

46.她决心今年再次竞选学生会主席。

47.你能提前为我安排一辆出租车吗?

48.但是这项研究并没有将其他诸如运输和冷藏之类的因素考虑进去。

49.这位飞行员利用想象力和经验完成了这次艰难的飞行。

50.人口增长应该与社会经济的发展相一致。

All the matter, space, and the time there ever has been or ever will be popped into existence 10 to 20 billion years ago.This tiny, supercompressed point—a “Singularity” in the jargon of physicists—was unimaginably hot and packed with energy. It burst forth in a titanic explosion and, expanding and changing ever since, it has become the universe that we—and who knows who else?—call home? If some cosmologists are right, it’s the only universe there ever has been, but there’s no way of knowing for sure.

Great art________moral teaching.

resulting     between     on      create        thanks         generator       in    charge      without          high

   The heat, which may result from sources such as solar heating or burning of fossil fuels, can be converted into electricity with a very (36) efficiency through a process known as thermionic conversion. Due to the many advantages that would have a system of this type which would be tradable(37) a large scale, many efforts have been for more than half a century to try to develop a practical thermionic generator, with little luck(38)—all attempts. However, such luck may change soon, (39)to a new design: an electronic thermal(40). The thermionic generators used the difference in temperature(41) a hot metal plate and a cold to (42) electricity. Basically, it creates a difference in electrical (43) between the hot plate and the cold. The(44) voltage drives an electric current, (45) the need for movement of mechanical parts.

Evidence has failed to______this assumption.

There is a supermarket_______our house.

Workers were told to______safety regulations in the factory.

He is always_______money before payday.

We should give up smoking______health.