The correct answer is b. decreased genetic difference between the two populations
Explanation:
The gene flow between two population always reduce the genetic difference between the two population because it increases the homogeneity between the population.
If there is greater gene flow between the two populations genes will be shared and transferred between the individual of two population which will make the two gene pool to become more and more similar.
This will increase the fitness of both the population because more allele will add to the two populations. Therefore the correct answer is b.
