Answer: A:A. Recessive alleles are expressed when there is one copy present.
Step-by-step explanation:
Individuals receive two copies of each gene called as allele. A recessive allele is the one which is not able to express when another allele of the same gene is of dominant type. Thus the phenotypic expression will be of the dominant type of gene. The recessive allele is only expressed when the other complementary allele is also of recessive type and thus the expression of recessive allele occurs in the phenotype. So, both alleles should be recessive to express a recessive phenotypic trait.