Why is John Marshall considered to be a national hero on the Mcculloch vs. Maryland Case? I just need a few summarized reasons

The decision in McCulloch v. Maryland was responsible for enshrining the "theory of implicit powers", used by the Federal Supreme Court on some occasions. Some of them will be dealt with in the final part of the article, especially those related to the investigative powers of the Public Ministry.

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."