All the genotype except aabb would be viable.
Step-by-step explanation:
The Dobzhansky model refers to the incompatibility of genes among species. The population of ancestral species was of the AABB genotype. But it is further divided into two populations.
One population involves a and A and the other has b and B. It has been found that the a and b are incompatible mutually. There is no presence of interaction between them in the actual species. So, the first genotype would not be viable in this model.