According to hoover et al. (1983), pedestrians who are more likely to another pedestrian pick up a dropped envelope are those who are closest to the person who dropped the envelope. physically resemble the person who dropped the envelope. just had their photograph taken. remain anonymous.

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."