The 20th century saw many great inventions,such as airplanes,motion pictures,television,telephone,computer,the Internet,to list just a few.Each of these inventions bears witness to the amazing advancements in technology in the past century.These inventions made our lives much easier and much more enjoyable.

　　However,progress in technology is always a double edged sword.People invented pesticides to kill pests but pesticides can pollute the environment by entering the water supplies and harming birds that eat the dead insects.Cell phone has greatly facilitated communication yet it has been proved that it poses danger to users' health.What's more,cell phones often go off during movies,concerts,classes,meetings,and libraries and create public nuisance.Automobiles have become an indispensable tool to the modern man but they consume great amounts of fuel,and create enormous environmental problems.Also,many people are killed in car accidents every year.Internet links tens of millions of people around the world but people are so addicted to the Internet today that they don 't go out and do exercises. 　

  　In a word,technology can be put to good use only when it's used properly.People often find it hard to balance the convenience brought by modern technology and its potentially harmful effects.I believe the average people should be educated about the potential harmness of technology and should always use it with a mind to promoting the teamwork spirit.