Answer
b.
Work Step by Step
If either parent were homozygous for the alleles for Tay-Sachs disease, then none of the offspring would have the disease because each offspring would inherit at least one normal copy of the gene, so the disease would not be seen in the children since the dominant normal gene would mask the defective gene.
However, if each parent were a carrier, meaning both parents are heterozygous, then any offspring they have would have a 25 percent chance of inheriting the disease because there is a 25 percent chance that any offspring they have would receive two defective recessive alleles, which would cause the defective allele to be expressed.
