What is sub-saharan africa a. the area of the african continent that is covered by the sahara desert b. the area of the african continent which lies north of the sahara desert c. the area of the african continent which lies north on the sahara desert

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."