A psychologist testifying in court feels it is his responsibility to correctly and clearly present scientific findings, even if this may lead to an unfair verdict by the jury. According to Saks (1990), such an expert fulfills the role of:.

the assessment of scientific validity of testimony before allowing it in trial.

Explanation:

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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."

this is not a question