What was Dorothea Dix known for? A. improving the conditions in Alabama prisons
B. improving the treatment of people who were mentally ill
C. improving the care for soldiers on the warfront
D. protecting the American wilderness

its c i google it wish u luck

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."

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