题目内容：
共用题干If you made a list of all the jobs performed by the different kinds of energy,you would fill many pages.
Nuclear energy is used in some areas of the United States.But there are dangers.Waste materials from nuclear______(51)would destroy life if they leaked______(52)the land.When nuclear energy is produced,a lot of______(53)is produced,too,50 a flow of lake or ocean water 15 used to cool the operations.Then the water______(54)to its source.If the returning water were too hot,it would destroy fish and other______(55).
Cow manure is being used to produce a kind of______(56).The manure from farms is put into a machine to convert it to a liquid.Then the gas 15 formed______(57)a natural process.If the converter were not 50______(58)at the present time,it would be used in many places to provide______(59).
Garbage has become an energy source.It______(60)to oil,steam,or electricity,or it is used on the land.
But recent______(61)about power supplies has led to increased interest in the use of wind______(62)a source of electrical power.Windmills are clean and they______(63)no waste.And they use a______(64)resource.Some scientists consider that wind energy systems can fulfill a valuable______(65)in meeting the energy needs of industrialized nations and of the developing world.
_________(60)
A:converts
B:is to convert
C:is converting
D:is converted
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