单项选择题

People communicate for many reasons. They communicate in order to give information, to ask help, to give orders, to 61 promises, to provide amusement, to express their 62 . Much of the communicating that people do is 63 to persuade someone to change his attitudes or the way he behaves. 　　The study of persuasion is interesting both on scientific and on practical grounds. On the scientific side, it helps us to understand 64 why people behave the way they do and why their 65 sometimes changes. On the practical side, an understanding of persuasive techniques would have obvious 66 to an advertiser, a politician, and educator--to anyone 67 job is to change what people think and do.It is probably not 68, therefore, that the 69 of research devoted each year to this topic has been growing even faster than the burgeoning rate of psychology as a whole. There have been literally hundreds of experiments on persuasive communication during 70 of the past decades.