In the Ethical Challenge Feature "Nonviolence: A Legacy of Principled Effectiveness," your text suggests that the proven effectiveness of nonviolence in achieving social change is, sadly, rarely effective in interpersonal situations.
a. true
b. false

False is the correct option.

Explanation:

The approach of nonviolence is very much effective.

Option B -- false

Explanation: We should be fully kept abreast that, In the Ethical Challenge Feature "Nonviolence: A Legacy of Principled Effectiveness," your text suggests that the proven effectiveness of nonviolence in achieving social change is, happily, and very effective in interpersonal situations. Therefore, based on the aforementioned question it's False

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."