$XII.$
1/ For a long time people have used water to power machines.
2/ Solar panels can be placed on the roof of a house and sun's energy will be used to heat water.
3/ We use energy from the sun, the wind and the water.
4/ Many countries have already been using solar energy.
5/ The earth's fossil fuels will be running out.
6/ We are looking for a cheap clean effective source of energy which doesn't cause pollution or waste natural resources.
