Answer :
D
Natural selection is the biological phenomenon in which the environment fits a population to its environment. The individuals that are better adapted to a particular habitat niche are a more competitive advantage in the struggle for resources and have increased chances of passing down their genes to the next generation.
Explanation:
Birds with stronger beaks out-compete the other birds for nuts and hard seeds hence dominate this niche. The birds with longer narrow beaks out-compete other birds for small insects and larvae hence dominate in this niche too. Over time the different subspecies are fitted into their niches by natural selection.
Learn More:
For more on natural selection check out;
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