Answer:
the color of someone's hair
Step-by-step explanation:
A is incorrect because heredity has nothing to do with who your best friends are. It is not something that is passed through generations. B is incorrect because again, where someone lives is not determined by their heredity. D is incorrect because someone's grades in school are determined by how much they're understanding the material. It has nothing to do with heredity. C is correct because depending on what genes you get from each parent can determine your hair color.
Hope this helps! :)