C. Provide one possible explanation for the change in bird numbers and beak characteristics.

Evolution

Explanation:

If there is an environmental stressor, then animals will evolve to overcome it.

Birds may begin producing more or fewer offspring depending on how much food is available. If there is more food available, birds will have more offspring. If there is less food available, birds will produce fewer offspring.

Beak characteristics change depending on food options, mating rituals, or environment. A bird will need a narrow beak for most bugs, but it will need a wider and stronger beak for nuts and seeds. A bird's beak may also be used to help interact with its environment. For example, a woodpecker has a strong narrow beak to help it break into tree bark to eat.

the solute can move "downhill," from regions of higher to lower concentration, relying on the specificity of the protein carrier to pass through the membrane. this process is called passive transport or facilitated diffusion, and does not require energy.