Fact 1: TV ads are becoming more and more ineffective, and the proportion of brand names that TV viewers can recall for promotion on TV is slowly decreasing. Fact 2: Television viewers recall the first or last advertisement in a series of commercial advertisements much better than they recall the advertisement somewhere in the middle. Which of the following options, if correct, fact 2 will most likely provide an explanation for fact 1. ['the average number of consecutive TV commercials is gradually increasing.', 'At present, the average TV viewer can only recall less than half of the brands he or she sees promoting.', 'the total time allocated to each group of consecutive TV commercials gradually decreases.', 'the number of groups that broadcast continuous advertisements on TV every hour gradually increases.']