When television first began to expand, very few of the people who had become famous as radio commentators were able to be effective on television. Some of the difficulties they experienced when were trying to【B1】themselves to the new medium were technical. When working on radio, for example, they had become【B2】to seeing on behalf of the listener. This【B3】of seeing for others means that the commentator has to be very good at talking. Above all, he has to be able to【B4】a continuous sequence of visual images which【B5】meaning to the sounds which the listener hears. In the【B6】of television, however, the commentator sees everything with the viewer. His role, therefore, is completely different. He is there to make【B7】that the viewer does not miss some point of interest, to help him focus on particular things, and to【B8】the images on the television screen. Unlike his radio colleague, he must know the【B9】of silence and how to use it at those moments【B10】the pictures speak for themselves. 【B1】