In which condition will a recessive trait appear in the phenotype?

Correct answer: When both factors are recessive

For a trait controlled by a dominant and recessive allele, the dominant allele masks the recessive allele in a heterozygote. The recessive phenotype appears only when the individual receives a recessive allele from each parent, giving a homozygous recessive genotype such as aa. Therefore option B is correct. One recessive allele with a dominant allele produces the dominant phenotype, and the other alternatives do not describe a valid allele condition for expression.