Why is power sharing important?

Power sharing is important because it reduces the possibility of conflict between social groups.

Power sharing ensures the stability of political order as social conflict often leads to violence and political instability.  

Explanation:

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."