The correct answer is option C, that is, structural adaptation.
All the species exhibit adaptations, which assist them to thrive and survive. Structural is one of the kinds of adaptations, these refer to the physical characteristics of an organism.
Structural adaptation refers to the feature in an animal or plant's body, which assists it to thrive in its surroundings. The examples are possessing the tendency to retain water, and camouflage that is protective coloration.