Several Cases of Children Growing Up in Extreme Social Isolation

Several cases of children growing up in extreme social isolation, documented by Kingsley Davis, suggest that:

A) most mental capacities, and perhaps even the ability to think, are learned through social interaction.
B) human intelligence is almost entirely determined by heredity.
C) the effects of isolation at an early age are easily reversible if caught in time.
D) the effects of extreme isolation in children are irreversible if the situation isn't corrected by the time the child is five years old.
E) Mead's view of the development of the self is flawed.