Question

an individual’s baseline odor, unique to only them, is known as their: individual identifier compound major histocompatibility complex subliminal descriptor scent

Explanation:

The major histocompatibility complex (MHC) is a set of genes that produce proteins influencing an individual's unique baseline body odor, which is specific to each person. The other options do not refer to this unique personal odor identifier.

Answer:

major histocompatibility complex