4．
阅读理解
New Energy in the Twenty-first
Century
Energy from wind
Wind is a kind of clean energy, and there is
lots of it, but, if there's no wind, there is no wind energy.
Energy from the water
When water from a high place to a lower place, it
can make electricity（电） without pollution. However,
people have to build dams（水坝） to use this energy, and
building dams is very expensive.
Energy from the earth
There is heat in the rocks under the earth. Scientists
use the beat to make geothermal（地热的） energy. This kind of
energy is cheap and clean, but it is only possible in a few places in the world.
Energy from the sun
Solar panels（太阳电池板） on the
roofs of house can tum energy from the sun into electricity. Solar power is
clean and plentiful（丰富的）. When the weather is bad, it
doesn't work.
