In this type of economy, economic decisions are made in the marketplace
according to the laws of supply and
demand.

the values of the selma marchers was to bring   their ability to vote into law. mlk was not hat march, which was protesting toward lbj

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."

well this isn't a question but if you are asking if it is true or false it is, true.