eli is afraid of bees, and has been ever since he was nearly stung by one a few months ago. lately, his father has been very distressed to see that eli is now afraid of any flying insect, even tiny ones like gnats. the fact that eli gets terribly afraid and runs to another room whenever he sees a flying "bug" demonstrates

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."