An 82-Year-Old Man Is Alert and Oriented and in Good

An 82-year-old man is alert and oriented and in good physical health except for some arthritic pain that "slows me down, but I just keep moving." He lives alone in an apartment in a senior citizen complex but enjoys the company of other residents and takes part in the social activities there. His lifestyle is an example of:

A) an exception to the expected norm.
B) the disengagement theory.
C) the activity theory.
D) the biological theory.