Advertisers are often interested in knowing things such as the age of the youngest child, the size of the family, and the family income. The age of the youngest child at home tells an advertiser where the family is in terms of its needs and obligations (i.e., toys, investments for college savings, clothing, and vacations). When the youngest child leaves home, the family's consumption patterns change. Advertisers like to track the age of the youngest child living at home and use it as a planning criterion. This is known as the _______________.
a. Identity
b. Family
c. Taste
d. Life-stage

Life-stage refers to the different phases of life that an individual passes through during the course of his/her life. These phases can refer to childhood, adolescence, adulthood, for example.

Each of these stages has different characteristics and different needs related to them.

In the example, advertisers are interested to know the age of the youngest child at home for example, because this gives information on what life-stage the family is at and what are their needs and obligations.

As the youngest child of a family grows older, the family needs change depending on this youngest child needs (while he/she lives in the same household as parents) and therefore it can give information to advertisers on which products are needed by the family and which of them are more feasible to be purchased.

Therefore, this approach is a life-stage approach.