Cystic fibrosis is an autosomal recessive disease where mucus develops in the lungs, liver and the pancreas. Which Punnet Square would have 25% of the offspring be homozygous dominant?

A)
B)
C)
D)

A

Explanation:

B and D are incorrect because 0% of the offspring would be homozygous dominant

C is incorrect because 50% of the offspring would be homozygous dominant

that leaves A as the only correct answer which makes sense because only the first square is AA which is 25% of the whole