The un security council's decisions depend entirely on the interests of its member states, and although security council resolutions in theory bind all un members, member states in practice often try to evade or soften their effect. these characteristics of the council are both examples of its

of what agreement it does not show

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."