Renewable EnergySources

Today petroleumprovides around 40%of the world's energy needs,mostly fuelling automobiles.Coal is still used,mostly in power stations,to cover one-quarter of our energy

needs,but it is theleast efficient,unhealthiest and most environmentally damaging fossilfuel.Natural gas reserves could plug some of the gap from oil,but reserves ofthat will

not last into the22nd century either.

Most experts predictwe will exhaust easily accessible reserves within 50 years.We could fasi reachan energy crisis.We need to rapidly develop sustainable solutions to fuel

ourfuture.Lesspolluting renewable energy sources offer a more practical long-termenergy solution.They may benefit the world's poor too."Renewable"refersto the fact that

these resources arenot used faster than they can be replaced.

The Chinese andRomans used watermills over 2,000 years ago. But the first hydroelectric damwas built in Englandin 1870.Hydroelectric power is now the most common

form of renewableenergy,supplying around 20%of world electricity. China's Three Gorges Dam,which hasjust been completed,is the largest ever. At five times the size of

the US's HooverDam,its 26 turbines will generate the equivalent energy of 1 8 coal-fired powerstations.It will satisfy 3%of China'sentire electricity

demand.Surprisingly,someargue that hydroelectric dams significantly contribute green- house gases.

In 2003,the firstcommercial power station to harness tidal currents in the open sea opened in Norway.It is designed like windmill,but others take the form of turbines.

As prices fall,windpower has become the fastest growing type of electricity generation-quadruplingworldwide between 1999 and 2005 .Modern wind farms consist of

turbines that gener-ate electricity.Though it will be more expensive,there is more than enough windto provide the world's entire energy needs. Wind farms come in onshore

and offshoreforms.They can often end up at spots of natural beauty,and are often unpopularwith residents.And turbines are not totally benignthey can interfere with radar

and leave asignificant ecological footprint,altering climate and killing seabirds.Migrating birds may have more luck avoiding them.Scotland is building

Europe's largestwind farm,which will power 200,000 homes.The UK's goal is to generate one-fifth of power from renewable sources,mainly wind,by 2020 .But this may

cause problems,be-cause wind is unreliable.

Which is thecountry with the first commercial power station that makes use of oceancurrents produced by tides?

A.China.

B. Norway.

C. England.

D. America.