Tortoises in the Galápagos Possessed Neck Lengths Unique to Each

Tortoises in the Galápagos possessed neck lengths unique to each island. Neck lengths appear to be an adaptation to which selective agent?

A) ease in finding pools of drinking water
B) type of vegetation available to eat
C) reproductive barriers used to produce offspring
D) defense against predators
E) male competition for females The neck length of tortoises on the various islands evolved in response to the vegetation available to eat. Some islands had only tall growing cacti while others had cacti growing low to the ground.