To Protect Our Public Home-the Earth

Many years ago,the sky was blue,the river wasclear and the air was fresh.There were countlessanimals and plants in our planet.Man enjoyed thebeautiful scenew and wonders given by nature,theearth Was full of life and vigour,people couldhardly imagine what the sand storm and acid rainwere,however,it is the true for it often attacks theearth and mankind and threatens our existence。