填空题

Energy from the Sun

Everyone needs and uses energy. If there were no energy, (46)
Most of the energy on this planet comes from the sun, but people do not receive that energy directly. It comes from different sources and in different forms.
Green plants convert the sun’s energy to food energy that animals and people use for life. The energy from animals has been used for hundreds of years to operate farm equipment and to pull carts, wagons , and other vehicles.
The sun’s energy takes water from rivers, lakes, and oceans and (47) When rain or snow falls on the land some of it flows into rivers and streams. This flowing water can be used to (48) Water can also be converted (更换) to steam, which produces energy to operate machines.
Winds also come from solar energy. Air that has been heated by the sun rises and creates winds. The process of winds has moved ships on the sea, ground grain, and brought water to the earth.
There is also solar energy in wood, oil, and coal. These fuels have been (49) People burn them to produce heat and to create power for machines. Oil and coal are used to produce electrical energy, too. And electricity produces light heat, and sound energy. In addition, electric power operates (操作) many kinds of equipment, tools, and machines, which make work easier.
If you made a list of all the jobs performed by the different kinds of energy, you would fill many pages . The need for power increases every day, and some sources of energy (50) So scientists and technicians are trying to find new ways to produce power.

• A. formed over many centuries from plants.
• B. returns it to the earth in the form of rain or snow.
• C. are being used up very quickly.
• D. there would be no life.
• E. produce mechanical energy and electricity.
• F. are being produced everyday.