Answer:
C.) 2
Step-by-step explanation:
Just a side note, I just assigned a random letter to work through this problem. It does not matter what you choose.
The carrier genotypes are Aa while any non carriers are AA, and any affected would be aa.
You would go through each of the pairs and do a pedegree to find out the genotypes of the offspring they produce. For 1 it would be a pedegree for Aa from the mom and AA from the dad. There offspring would be 1/2 Aa and 1/2 AA.
For number 2 it would be Aa for the mom and Aa for the dad. There offspring would be 1/4 AA, 1/2 Aa, and 1/4 aa.
For number 3 the mom would have AA and the dad would be aa. There offspring would be 4/4 Aa
For number 4 the mom would be Aa and the dad would be AA. There offspring would be 1/2 AA and 1/2 Aa.
Group #2 are the only set of parents that would produce a offspring that would be affected by the genetic condition, so the answer is C