Callie, age 11 months, went to the circus with her mother. When a clown came bouncing up to Callie's stroller, Callie was anxious looked at her mother. When Callie's mother began to laugh at the clown, Callie joined in the laughter. Callie's behavior is called_______
a. affective regulation.
b. social referencing.
c. stranger anxiety.
d. bonding dependence