The body part that adapted to help the birds eat different things is B. Beak.
Birds' beaks have evolved to help them eat different types of food. For example, birds with long, thin beaks are better suited for catching insects, while birds with short, strong beaks are better suited for cracking nuts or seeds. In the case of the birds in the forest, one group of birds have adapted to have beaks that are better suited for eating large berries, while the other group of birds have adapted to have beaks that are better suited for eating tiny seeds.