[A] Jean Piaget and Lev Vygotsky would explain this as egocentric nature of the child's thoughts.
[B] Jean Piaget would explain this as egocentric speech, while Lev Vygotsky would explain this as the child's attempt to regulate her actions through private speech.
[C] Jean Piaget would explain this as social interaction, while Lev Vygotsky would explain this as an exploration.
[D] Jean Piaget and Lev Vygotsky would explain this as the child's attempt to imitate her mother