Which of the following occurrences would most likely result in an increase in allele frequencies in a population?

a. A disease killed off 3/4 of the members of a herd of wildebeest.

b. A third of the baby sea turtles that hatch are eaten by predators.

c. A school of trout that were separated by a dam.

d. A flock of ducks joined another group living near a lake.