In His Observations of the Tortoises on the Galápagos Islands,Darwin

In his observations of the tortoises on the Galápagos Islands,Darwin concluded that

A) long-necked tortoises acquired their long necks by stretching to reach vegetation.
B) those tortoises were not related to tortoises on the mainland.
C) each island species was derived from a different mainland ancestor.
D) where vegetation was sparse, long-necked tortoises were favored because they could reach higher to get their food.
E) short-necked tortoises had resulted because of spontaneous generation.