Which of the following is not an example of ageism?
a. advertisements that use elderly people to sell health related devices
b. an older adult portrayed as a positive role model
c. news coverage focusing only on the negative aspects of aging
d. a television show portraying elderly citizens as cranky and unproductive

An older adult portrayed as a positive role model is not an example of ageism. So the correct option among all the options that are given in the question is option "b". Ageism is actually a social attitude that defines the way people look at older people and stereotypes them as lazy, useless, strong or in any other way. Ageism is also a part of the way where people feel that they can treat any elderly people in demeaning ways.