The answer is letter A.
Social development refers to the manner on how infants and children relate to other people. As babies grow into mature individuals they are exposed to different environments which force them to interact. They tend to not only remember their family circles but also other people that have been introduced to them get retained in their memories.
Eventually these interactions affect how an individual grows and processes things that are around him. Then later on they develop analyzing capabilities that allow them to react to different stimuli in their environment.
