An Elk Herd Is Observed Over Many Generations

Multiple Choice

An elk herd is observed over many generations. Most of the full-grown bull elk have antlers of nearly the same size, although a few have antlers that are significantly larger or smaller than this average size. The average antler size remains constant over the generations. Which of the following effects probably accounts for this situation?

A) directional selection
B) stabilizing selection
C) a bottleneck effect that resulted in low genetic diversity
D) a high rate of gene flow