Which of the following scenarios would prevent a population from being in Hardy-Weinberg equilibrium?

A. The population will fall out of Hardy-Weinberg equilibrium if natural resources such as food are limited.
B. The population mates at specific times of the year, causing the population to fall out of equilibrium at that time of year.
C. The population is stable, but younger generations of the population have a different allele frequency.
D. The population is evolving, and natural selection is favoring one allele over another.