Many large cities are not so beautiful. There is a lot of trash in the streets. 1 , some of them can be 2 . If people want to 3 the problem, they should do it right now. They must work out 4 of makeing use 5 garbage. 6 this way, some good things will not be thrown away 7 waste. When a car 8 too old, it may not run any more. But the metal that the car was made 9 is 10 good. We can use it to make something 11 . When a bottle is 12 , it goes out in the trash. But bottle glass can be made into sand and used to 13 streets. Garbage from 14 can be changed into fertilizer. It is cheap and 15 . Garbage can also be used to make 16 blocks. These blocks are 17 with concrete in a while. Now, more and more machines are designed 18 that. Some day, people will watch films in a beautiful 19 and it has been built out of garbage. Besides, in the future, buildings, roads, and cities may be made 20 barbage. But so far, building beautiful cities out of garbage is only a dream.