After a rapid change in climate, one population of bird quickly adapts to the change, but others in the area do not. What could you conclude about the quickly adapting population?

A) They had a greater need to evolve than the other population.
B) They already had some alleles in their genome that were adaptive in the new environment.
C) They reproduced more slowly than the non-adapting population.
D) They had a higher rate of mutation than the other population.