The alleles to choose a good male c. The fitness of the mother is increased only if the daughters reproduce. There will reach a point at which no male can survive the handicap. At that point the handicap can get no larger. The environmental conditions change gradually through space.
Examples are rainfall and temperature b.
The founding population has a different allele frequency than the main population. Having a different gene pool increases the rate of differentiation. In frequency dependent selection, which phenotype has the highest fitness. The least common. Least frequent etc.