yesterday,we didn‘t have cars.but today we have.yesterday,we didn‘t have tv sets.but today we have.yesterday we didn‘t have computers.but today we have.during the hundreds of years,how fast the world has changed!that‘s really a myth.

　　though the new world brings us a convenient life.it also brings more problems.for example,population,resources ,environment and so on.

　　we know that the world‘s population is growing faster and faster. it‘s more than 6 billion now.it‘s a very big number.we can say the number of world‘s population is like the number of the stars in the universe.and if it goes on like that,i can‘t image what will happen.

　　as the second problem,the world is short of resources now.in daily life,we need water,rock oil,coal and other things.day after day,the resources disappear fast.and they won‘t appear.because most of them are not renewable resources.