Which variable is the best predictor of one's own class position as an adult?

Possible predictor of one’s class position as an adult could be their socioeconomic status. Socioeconomic status refers to a person’s position with regards to income, education and occupation determined by academic and work experience, and their social relations. Today, the factor of socioeconomic status highly reflects a person’s sense of achievement and fulfillment in life although discounting the significance of psychological and other factors such as awareness and self-actualization to determine a person’s status. 

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; self-serving bias;