Cosmo, Age Three, Has Always Been Cooperative About Going to Bed

Cosmo, age three, has always been cooperative about going to bed at night. Then the family takes a trip and stays with relatives, where Cosmo 's cousin, Wanda (also age three) , has a royal fit at bedtime. Cosmo watches while Wanda's parents read her extra stories and bring her a glass of juice to calm her down. After Cosmo and his family return home, Cosmo begins to throw tantrums at bedtime. Cosmo's change in behavior is best explained by

A) observational learning.
B) classical conditioning.
C) sensorimotor stage thinking.
D) latent learning.