You're watching a veterinarian perform a surgical procedure to determine the sex of a bird. A male bird's testes are difficult to find because they're A)

external.

B)

everted.

C)

internal.

D)

vestigial.

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.

the sun's light combined with the visible wavelenghts form what is called ultraviolet radiation, which are the long waves at the end of a visible light sprectrum.

hope it ,

bioteacher101