Answer:
The increase in the average beak depth caused by both an increase in large-beaked finches and by a decline in small-beaked finches
Step-by-step explanation:
The increase in the average beak depth is caused by both an increase in large-beaked finches and by a decline in small-beaked finches. All the small-beaked finches got disappeared. As a result, only large-beaked finches were left. The drought decreased the number of seeds such that large-beaked finches could eat the larger seeds to survive.