n a(n) , one or more variables are identified and controlled or manipulated so that data can be obtained about how they influence the variable of interest identified first. a. variable study b. experimental study c. observational study d. categorical study g

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."

answer; criminal law;

answer; all of the above are correct;