电磁波的发现揭开了现代通信的新纪无．电磁波已成为人类文明的重要标志．但值得注意的是，电磁波也会造成______．
造成电磁波污染的原因是多方面的．随着城市的发展，市区扩大，建筑用地日趋紧张，使原本处于郊区的大功率电磁发射台．电视广播发射台站逐渐被新建居民区包围，卫星通讯的发展．使得城市出现众多的卫星地面站．有的地区发射天线过密，移动通讯技术迅速发展．其电磁波信号采用直线传播，在市区高层建筑上架设许多起联络作用的基地台站，天线林立，形成相互间的交调干扰；还有部分架设不合理的天线对附近高层住宅居民产生电磁波污染，传输电力的超高压输电线路和城市交通运输系统使电磁污染增加．另外，家用电脑、彩电、音响、微波炉、电磁灶、无线手机、电热毯都会辐射出电磁波，也会造成环境电磁污染．
故答案：污染．
| 完形填空 | ||||
Val entine's Day was the time my father chose to show his love for the special people in his life.Over the years I fondly (天真地) thought__1__him as my "Valentine man". My first recollection of the__2__he could bring to Valentine's Day came when I was six.That morning at the breakfast table I found a card and a giftwrapped package at my chair.The card was__3__"Love, Dad" and the gift was a ring with a small piece of red glass to__4__my birthstone, a ruby (红宝石). There is__5__difference between red glass and rubies to a child of six, and I remember__6__that ring with pride that all the cards in the world__7__not surpass (超越). __8__I grew older, the gifts gave__9__to heartshaped boxes filled with my__10__chocolate and always included a__11__card signed "Love, Dad". In those years my thankyou became__12__of a perfunctory (敷衍) response.The cards seemed less__13__, and I took for granted that the Valentine would__14__be there.I had__15__my hopes and dreams in receiving cards and gifts from "significant others" and "Love, Dad" just didn't seem quite__16__. final card remains on my desk today.It's a__17__of how special fathers can be and how important it has been to me over the years to know that I had a father who continued a__18  __of love with simpleacts of understanding and an ability to express happiness over the people in his life. Those things never__19__, nor does the memory of a man who never__20__being my valentine. | ||||
|