Brent is an emerging adult studying cross-cultural anthropology, which gives him the opportunity to examine a range of variable perspectives regarding marriage and family structures and attitudes. This kind of thinking is best described as:

realitivistic

Explanation:

Realitivistic thinking: In cognitive psychology, the term "realitivistic thinking" is described as a phenomenon through which an individual believes that the reality and the cognition related to it is somewhat relative and therefore it relies on the individual's "adopted perspective". In the context of "realitivistic thinking", an individual's reality is considered as constantly and naturally dynamic and variable yet viewpoint is determined by situational context, culture, entity's cognitive capabilities, language, circumstances, etc.

In the question above, the kind of thinking is best described as "realitivistic thinking".

the declaration states, “we hold these truths to be self-evident, that all men are created equal, that they are endowed by their creator with certain unalienable rights, that among these are life, liberty, and the pursuit of happiness….”