C. The average number of hours per day that people spend watching television is decreasing.看电视得总的时间减少了,对广告的接触时间自然减少,则效果减弱。
D. The average number of clusters of consecutive commercials per hour of television is increasing. 同意bomber所说的,因为单位时间内广告总量增加了,边际效用递减,则对单个广告而言,被记住的可能性就小了,则效果减弱。
D. The average number of clusters of consecutive commercials per hour of television is increasing. 同意bomber所说的,因为单位时间内广告总量增加了,边际效用递减,则对单个广告而言,被记住的可能性就小了,则效果减弱。