Which characteristic is most likely to be determined by biological factors?

The characteristic that is most likely to be determined by biological factors is physical appearance. This includes traits such as height, body shape, skin color, and other features that are primarily influenced by genetics. Biological factors, including the genes inherited from one's parents, play a substantial role in determining these physical traits from the moment of conception.

While personality traits and intelligence also have biological underpinnings, they are more complex and can be significantly influenced by environmental factors, experiences, and learning. Hair style is predominantly a personal choice and influenced by cultural or social factors rather than biology. Therefore, physical appearance stands out as being the most directly tied to biological determinants.