Wind power is a very clean source of energy． This is how wind power works． Wind makes windmills spin （旋转）． When the windmills spin， they make electricity． Then we can use the electricity．

    A lot of people think that wind power is new， but that's not true．For thousands of years， people have used wind to sail boats and move water． We still do those things today， but these days we mostly use    wind power to make electricity．

    Wind power is a very popular source of energy． Most people think that we should use it more and more． First of all， it's clean． Windmills don't pollute the environment at all． Second， we can use wind power forever． After all， we will always have wind． Also， wind power is cheap， and it's getting even cheaper．

    A lot of people don't understand wind power very well． They believe that there are problems with wind power， but many of those problems are not real． For example， some people say that windmills are dangerous for birds． They used to be true， but it isn't true anymore． Old windmills killed birds because they spun very fast． New windmills spin slowly， and they aren't dangerous for birds．

    However， there are real problems with windmills． One problem is that many people think windmills are very ugly． This is a problem for people， because windmills are often in very pretty areas． Also， wind doesn't blow all the time， so we can't use wind power all the time． Finally， windmills are noisy．

    Wind power is becoming more and more common． Right now， more than 80 countries use wind power． About 2.5 percent of the world's power comes from the wind． For some countries， that number is a lot higher． Wind power gives Denmark more than 25 percent of its electricity．

（1）Why DON'T new windmills kill birds？ Because　　．

A． birds don't fly near them

B． they spin slowly

C． they are shorter than old windmills

D． new windmills don't spin

（2）When did people start using wind power？　　

A． About 25 years ago．

B． About 80 years ago．

C． About 500 years ago．

D． Over 1，000 years ago．

（3）　　， so we CAN'T use wind power all the time．

A． Windmills break all the time

B． We can't use windmills at night

C． Windmills are too expensive to use all the time

D． Wind doesn't blow all the time

（4）What does the article say about wind power？　　

A． Most people don't like it．

B． It's getting cheaper．

C． Denmark doesn't use it．

D． It's getting more expensive．

（5）What is the best title for the passage？　　

A． Expensive Windmills

B． Cheap and Clean Energy

C． Popular and Clean Wind Power

D． Dangerous Birds