B. It sped up evolutionary change by increasing genetic variation.
Evolution works when organisms with genes that are better suited to the environment pass on their genes to future generations.
Sexual reproduction sped up this process because it allowed for genetic variation as genes from the two mates would be passed on the next generation instead of one organism as had been the case with asexual production.
With genes from both mates mixing up and going into the next generation, more genetic variations were produced which allowed for the organisms to better adapt to the environment.