Answer:
c. participant observation
Step-by-step explanation:
Participant observation -
It is the observation method , in which data is collected by using ethnography and qualitative research .
This method is used in many field like the sociology , social psychology , human geography , communication studies , European ethnology , cultural anthropology .
The main focus of this method , is to achieve a intimate and close familiarity .
hence , from the question information , Matthew is employing the c. participant observation .