C is the right answer.
There is 25% represents the risk for this couple’s next child to have Tay-Sachs disease.
Tay - Sachs, a lysosomal storage disease inheritance pattern is Autosomal Reccessive.
Both parents are carriers of this recessive gene, which means that there is 25% probability that every child born will have this disease and there is 75% risk that each child born will be a carrier of this disease.
