Identify the topic sentence in each of the following paragraph(请找出下列段落的主题句) We now have, as a result of modern means of communication, hundreds of thousands of words flung at us daily. We are constantly being talked at, by teachers, preachers, salesman, public officials, and motion-picture sound tracks. The cries of advertisers pursue us into our very homes, thanks to the radio – and in some houses the radio is never turned off from morning to night. Daily the newsboy brings us, in large cities, from 30 to 50 enormous pages of print, and almost three times that amount on Sunday. We go out and get more words at bookstores and libraries. Words fill our lives.