Science and technology have been bringing human beings tremendous benefits. thanks to science and technology, we now live comfortably and conveniently in houses furnished with air conditioners, refrigerators, washing machines and televisions etc. thanks to science and technology, we can eat fresh vegetables all the year round. thanks to science and technology, we can travel tong distances in the fraction of a second on planes, trains and cars. thanks to science and technology, we wear clothes with synthetic materials which can not easily be worn out. however, science and technology have also brought us a tot of disasters. first, because of the many breakthroughs in the field of medicine, people are now living much longer than they used to. as a result, the population of the world is increasing, causing lots of problems. second, because of the development of industry, lots of the wastes from factories pour into the air and rivers, causing pollution of all kinds. third, some terrorists are using science and technology against mankind. they use biological, chemical and unclear weapons to threaten world peace...So it's urgent that we find ways to solve these problems. but we should not stop the development of science and technology because of these disasters they bring, just as we should not give up eating for fear of choking. in addition, we should make some rules to regulate our actions. as long as we use science and technology in a proper way, they may bring us even more benefits.