Most of us have three meals a day .We take food for granted(想当然)。And we don't think about it. 1 experts argue a food crisis(危机)is coming.This crisis is going to make us 2 the way we think about food.

 Food is in great need 3a growing of world population.By 1960,the population was three billion.It doubled to six billion by 1999.By 2050,this planet will need to  4 at least nine billion people.As a result,the food prices get higher and higher.

 So,what can a   5 ,crowed world do?One suggestion is to eat less meat.Meat uses more natural resources(资源)than grains(谷物) .It requires more  6  to produce one pound of meat than to produce one pound of grain. It also requires between 5 and 10 times more water than vegetables. So ,eating less meat will  7  more land for farming,and it will save water.

 To eat less meat,people will need to change their eating habits. That will not be easy. Americans, for example,have 8 loved meat.  In general, They eat twice as much meat as people in other countries.At the same time,in developing countries like China and Brazil,sales of meat have doubled in the last 20 years.   9  will double again by 2050.Growing need of meat wil continue to put pressure on natural resources.

 World  population is increasing,resources are becoming fewer,and food prices are rising.Therefore, we need to rethink what  we eat every day. For meat lovers, we don't  need to give up meat  10 .But we need to eat more grains and less meat.

    Fire can help people in many ways. But it can also be very harmful.

Fire can keep your house 1, give light and cook food. But fire can burn things 2 . Big fire can burn trees, houses, animals and people.

    Nobody knows how people began to use fire.  But there are 3interesting old stories about how a man or a woman started a fire. One is4 a man. The man 5 a very long time ago. He went up to the Sun and 6 fire down.

    Today people know how to make a fire with matches(火柴). Children sometimes 7 to play with them. But matches can be very dangerous. One match can burn a piece of paper, and 8 it can burn a house. A small fire can turn into a big fire very quickly. So you   9 be careful with matches.

    Be careful with fire, and it will 10 you. But if you aren't careful with fire, it may hurt you.

    Can you imagine that we could build a beautiful city with rubbish? Maybe you will think it is1. However, it can be true! Nothing is a waste if we have a creative mind. Let me show you something about2rubbish.

    Sometimes we can see tons of rubbish in the streets, on the roads, near the buildings... here and there. Many large cities became so ugly3it. Nobody likes rubbish, but in fact, some rubbish can be used again. All of us want to solve the problem, we must do something to4rubbish. We should take action from now on.5, some good things will not be wasted.

    Do you often throw away things you don't need any more? Have you ever thought about how these things can actually be put to good use? For Example, when a car gets too old, it may not run any more. But we can use the metal of the car to make something else. When a bottle is empty, it6as waste. You don't know bottle glass can be made into sand and used to build streets. Rubbish7food can be changed into fertilizer to make plants grow better. It is cheap and safe. And other rubbish can also be used to make building blocks. Now,8machines are designed for that.

    9, people will watch films in a beautiful cinema which is built out of rubbish. Besides buildings and roads, cities may be made from rubbish. But so far, building beautiful cities made from rubbish is only10.

    Some day little cars may take the place of today's cars. If everyone 1 such a little car in the future, there will be less 2 in the air. There will be more parking places in the cities, and the street will be 3. Now the space for one car of the usual size can 4 more than one such little cars. Driving will be 5, because these little cars can go only 50 kilometres an 6. The future cars will be fine for going around the city, but they will not be 7 for going far away. The little cars 8 only two batteries, one battery for the motor, and the other for the horn (汽车喇叭) and the lights. If we still 9 the big cars along with the small ones; we will need to 10 two kinds of roads. That is, there will be some roads for the big fast cars and other roads for the smaller and slower ones.

The first astronauts

    Since the earliest times, people have looked up at the stars, the moon and the planets. Today people use modern machines 1at the sky. This is very different from the situation2years ago when people could only use their eyes. Perhaps they dreamed of3the universe.

    When did humans first go into space? The story began not so very long ago, 4the first astronauts were not people-they were animals.

Scientists wanted to make travelling to space as 5 as possible for humans. So they decided to experiment with animals and test6 in spaceflights. Insects, mice, frogs, dogs and monkeys were some of the animals7first went into space. Many of them 8, but they helped to make space travel safer for humans. For their great service, we 9forget these animals.

    Albert Ⅱ was the first monkey to go into space in 1949. Sadly he died 10 his spaceship landed back on Earth.

    11 the result was different for Ham the Monkey. His story ended happily when he return to earth12very good health.

Scientists wanted to know the answer to the important question: could 13 animal like Ham do the same things in space as he could do on Earth? The answer came when Ham 14 into space in 1961. Yes, he did everything well and lived for 15 16 years