Concept:Variation refers to differences that exist between individuals of the same species.
It can be morphological, which involves physical structure, or physiological, which involves body functions and biochemical processes.
Explanation:The ability to taste phenylthiocarbamide, commonly known as PTC, depends on a specific taste receptor in the body.
This ability is not visible as a structural or external difference, so it is not morphological variation.
It is also not an adaptation because it is not an acquired trait developed for survival; instead, it is a naturally occurring genetic difference.
Since tasting PTC reflects a difference in how the body functions and responds to a chemical stimulus, it is classified as physiological variation.
Answer:B. physiological variation