which of these best demonstrates natural selection

A. a population of mice grow increasingly larger because the predators moved away from the area
B. The pelvic bones and snakes have grown smaller because they do not have legs.
C. A population of flowers takes over certain area because they attract the most bees for pollination. D. The human pendants has shrunk in size overtime because it is not used.

B. The pelvic bones in snakes have grown smaller because they do not have legs. This is a clear example of natural selection as the snakes with smaller pelvic bones were able to move more effectively and survive, passing on their genes to future generations.