Scientists observe a population of squirrels over a long period of time. The scientists note that after the populations are able to live together, the black and the brown squirrels are not able to produce fertile offspring. Which explanation best supports the scientists’ observation? A. The squirrel population experienced more mutations living together than living.

B. The squirrel population did not have enough genetic variation to produce fertile offspring.

C. The squirrel population divided into dominant population and a recessive population of one species.

D. The squirrel populations on either sid eof the river did not experience gene flow and became two different species.