Seeds are the major source of food for finches. Drought increases the number of large seeds and decreases the number of small seeds available to the finches. During periods of drought, only the finches with large beaks will be able to crack and eat the large seeds.
The answer among the given options is A, because the adapted finches with larger beaks will be able to survive the period of drought and a large beak does not necessarily mean it cannot consume smaller seeds.
