The most accurate answer is:
B. The mutation changed the structure of the genes, which changed the structure of the proteins. This change affected the function of the proteins, which caused the cat to have albino traits.
This option correctly describes the process by which a mutation in the genes can lead to changes in the proteins produced, which in turn affects their function and results in the observable trait of albinism in the cat. Albinism is specifically tied to the function of proteins involved in pigmentation.