Clark's eyes are brown in color. However, both his parents have eyes that are blue in color. According to the dominant-recessive genes principle, the most likely reason for Clark's eyes being brown in color is that:______

a. Clark's family history shows that the family has a dominant gene for brown-colored eyes.
b. Clark's parents are carriers of genes contributing to brown eyes.
c. Clark's parents are both carriers of genes contributing to blue eyes.
d. Clark's grandparents had brown-colored eyes.