Aboxer suddenly begins experiencing wild mood swings and bizarre behavior. a neuroscientist determines that the boxer has traumatic brain injury probably caused by numerous concussions. the neuroscientist then studies the brain functioning of the boxer in great detail using fmri brain-imaging techniques to learn more about concussions. this represents a(n):

The scenario above is best described as a case study. A case study is being defined as a record or a process by which a researcher made use of in being able to consider detailed information for the purpose of being able to develop a particular group or person or even a situation.

what words? are you talking about to complet what sentence

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."