Peter and His Father Were at the Doctor's Office

Peter and his father were at the doctor's office.Because Peter's father looked comfortable and happy when the doctor entered the examining room,the baby accepted the doctor's greeting with little fuss.Peter was at least ________ months old and was demonstrating ________.

A) 12; schematic learning
B) 9; deferred imitation
C) 10; social referencing
D) 18; discriminatory perception