Final answer:
After 5 years of plentiful rain, the finches on Daphne Major would likely experience a decrease in beak size due to natural selection and competition for food.
Step-by-step explanation:
After 5 years of plentiful rain, the finches on the Galápagos island of Daphne Major would likely experience a decrease in beak size. This is because during periods of plentiful rain, large seeds with hard cases become more available, which are successfully eaten by birds with large and broad beaks. As a result, the birds with smaller beaks would have a disadvantage in obtaining food, leading to a decrease in their population.