Biological traits generally follow a geographic continuum, also called a cline. how does this relate to the concept of race?

From an anthropologist's point of view, the concept of human diversity is inappropriately attributed to race, while Cline is the right concept to classify them.

Explanation:

First of all, from an anthropologist's perspective, the concept of different human races is just incorrect because characteristic variances don't specifically distinguish one human race from another. In this perspective, there is only one human race because we don't have significant differences to distinguish one trait from the other. So, the concept of "cline" is better to classify different human characteristics.

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."