79． Fire can help people in many ways.But it can also be very harmful.Fire can heat water，warm your houses，give light，and cook food.But fire can burn things too.It can burn trees，houses，animals，or people.Sometimes big fires can burn forests.
Nobody knows for sure how people began to use fire.But there are many interesting，old stories about the first time a man or woman started a fire.One story from Australia tells about a man very，very long time ago.He went up to the sun by a rope and brought fire down.
Today people know how to make a fire with matches.Children sometimes like to play with them.But matches can be very dangerous.One match can burn a piece of paper，and then it might burn a house.A small fire can become a big fire very fast.
Fires kill many people every year.So you must be careful with matches.You should also learn to put out fires.Fires need oxygen.Without oxygen they die.There is oxygen in the air.Cover a fire with water，sand，or in an emergency，with your coat or something else.This keeps the air away from a fire and kills it.
Be careful with fire，and it will help you.Be careless with fire，and it will burn you.
（1）Which is true？
A.We are not sure how people started to use fire.
B.It is an Australian who started a fire.
C.We know how people began to use fire.
D.Nobody knows how to make a fire.
（2）Children mustn't play with matches because
.
A.they don't know how to make a fire with matches
B.it is not interesting
C.matches can be dangerous
D.matches burn a house
（3）If you are going to put out a fire，you
.
A.must be careful with matches
B.ought to know it can be harmful
C.have to cover it with water only
D.should keep air away from it
（4）What is the main idea of the passage？
A.Fire can help people in many ways.
B.Fire can be both helpful and harmful.
C.Fire can burn things and people.
D.We must be careful with matches.
