A population of hummingbirds feeds exclusively on nectar from orchids. Two species of orchids exist in the hummingbirds' habitat. One orchid species has long tubes to store nectar while the other has short tubes to store nectar. The hummingbirds have a range of beak lengths, and the beak length determines which nectar tube an individual can feed from. This population of hummingbirds is splitting into two phenotypic groups. What scenario best explains why the population is diverging?

A.
Hummingbirds with shorter or longer beaks can feed from one of the available orchids, but hummingbirds with intermediate beak lengths cannot feed from either.
B.
Hummingbirds with the longest beaks are better adapted to the environment compared to hummingbirds with short and intermediate length beaks.
C.
Hummingbirds with intermediate beak lengths can feed from both species of orchid, but the individuals with the shortest and longest beaks can each only feed from one species.
D.
Hummingbirds with short beaks only mate with individuals who have long beaks, ignoring individuals with intermediate and short beaks.