15. A human baby boy inherits a recessive allele from his mother In which circumstance would he most likely show the trait coded for by the recessive allele? A The baby inherits the dominant allele from his father B The allele is on an autosomal chromosome and the baby is a twin C The allele is on the X chromosome D The allele is on the Y chromosome.

## Step 1
The problem is about understanding the inheritance of traits in humans, specifically focusing on the inheritance of recessive alleles.

## Step 2
Recessive alleles are traits that are expressed only when two copies of the allele are present. This means that the trait will only be visible if both parents pass on the recessive allele.

## Step 3
In the case of a male child, he has only one X chromosome, which he inherits from his mother. This means that if the recessive allele is on the X chromosome, the male child will express the trait coded by the recessive allele.

## Step 4
Options A, B, and D do not guarantee that the recessive allele will be expressed. For example, if the dominant allele is inherited from the father (option A), the recessive trait will not be expressed. Similarly, being a twin (option B) or having the allele on the Y chromosome (option D) does not guarantee the expression of the recessive trait.