Joaquin believes that older adults deliberately withdraw from social contact with individuals peripheral to their lives while maintaining or increasing contact with close friends and family members with whom they have had enjoyable relationships.
He is a proponent of _____.

1) activity
2) selective optimization with compensation
3) socioemotional selectivity
4) social discontinuity

Socioemotional selectivity is defined as the theory in which a person's realization about the future is limited and thus accordingly related aim, cognitive processing and choices are determined. It is the theory of motivation based on life span.

According to the question, Joaquin is believing socioemotional selectivity in which a person choose the priority according to the life span such as older adults value living their lives rather than making social contacts.

Other options are incorrect because activity is performance of some act and social discontinuity is withdrawing from social events at certain time.Selective optimization with compensation is improving the health of adults and older people.Thus the correct option is option(3).