If an individual is heterozygous for a particular trait,
a. each parent contributed a different allele for that trait.
b. each parent contributed the same allele for that trait
c. one parent contributed two different alleles for that trait.
d. one parent contributed two copies of the same allele for that trait

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; group behavior;

answer; becoming friends with her roommate and joining the debate team; sarah's making friends with her roommate and joining the debate team are examples of relational needs