Dr. Mendez has always followed the works of psychologist William McDougall. Like McDougall, Dr. Mendez believes that people are born with predetermined sets of behaviors, which help them survive. Dr. Mendez is most likely a proponent of:

d. i assume the underlined word is "role." reformat if it isn't.

explanation:

role is closest to part because when replacing words, "playing a vital decision," "playing a vital activity," and "playing a vital dollar" don't make logical sense. the only meaningful choice is "playing a vital part."

this fits one of merriam-webster's definitions of role: "a function or part performed especially in a particular operation or process."

answer; the trial de novo

answer; self-serving bias;