Which of the following scenarios refutes the argument that genes are entirely internally influenced?

A. Patrick possesses a gene for brown hair, but his children have blond hair.
B. Cindy possesses a gene for freckles, but she uses makeup to cover them up.
C. Margaret possesses a gene for melanoma, so she chooses to stay out of the sun.
D. Charles possesses a gene for Alzheimer's, but he has not yet experienced symptoms.