Final answer:
Option C, a child living alone in the woods, is what best depicts a feral child, as they grow up isolated without human contact or language and mimic animal behavior, crucial to understanding child development.
Step-by-step explanation:
A feral child is defined as a young human who has lived isolated from human contact, often with little to no experience of human care, love, or social behavior, and, crucially, no language. These children tend to grow up without the nurturing that is considered necessary for a 'civilized' child's development, mimicking the behaviors and movements of animals rather than people and often inventing their own ways of communication. Out of the options presented, option C., a child living alone in the woods, unable to speak, walking on all fours, and impervious to the cold, is most representative of what depicts a feral child.
Such children provide extraordinary case studies for researchers, like the well-known case of Genie. Her extreme neglect offers insights into the critical role social interaction and stimulation play in child development. Hence, researchers often use these unique cases to gain valuable understanding of human development and socialization.