Which country had and does have the highest intelligence people overall history, around the globe?

The country that had and still have the highest iq in both present and  past is Singapore. With a rate of 108

:)

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."