Marketers can group people in a number of ways, including by birth date. However, the following combination of groups has proven to be more effective: $\_\_\_\_\_\_\_\_.$

Select one:

a$.$

income, lifestyle, life stage

b$.$

profession, common values they seek in products they buy, lifestyle

c$.$

lifestyle, life stage, common values they seek in products they buy

d$.$

place of residence, life stage, lifestyle