An isolated population of island rabbits is in hardy-weinberg equilibrium until a storm floods the island, drowning many of the rabbits. after some time, the allele frequencies in the population start to evolve. which of the following conditions may be the cause of this departure from hardy-weinberg equilibrium? the population no longer has genetic mutations. the population now lacks any sexual selection. the population size is now not large enough. the population became isolated from other populations.

The answer is;

The population size is now not large enough.

This is referred to as a bottleneck effect. Due to the calamity wiping out a huge chunk of the population, the variation in the population reduces. The genetic drift is, therefore, more pronounced on the small population than big population due to reduced sampling. The reduced genetic variation makes the population vulnerable to environmental changes because natural selection will not find a wide variation of genotype to act upon.

If I am correct, C, "The population size is now not large enough." would be the correct answer.