A gene that is not expressed when paired with a dominant allele is called a/an trait
mutation
base pair
recessive allele

recessive allele

Explanation:

A dominant allele is one that always determines the phenotype when present. On the other hand, a recessive allele is one that is not expressed when its paired allele is dominant. With eye color, the brown eye allele is dominant to the blue eye allele.

Recessive allele

Explanation:

A dominant allele is one that always determines the phenotype when present. On the other hand, a recessive allele is one that is not expressed when its paired allele is dominant. With eye color, the brown eye allele is dominant to the blue eye allele

the answer is d.) homologous; have mammary glands