When Kristen Asks Her Grandmother for a Cookie, Her Grandmother

When Kristen asks her grandmother for a cookie, her grandmother usually gives her one. Last week at the park, Kristen's mother was embarrassed when Kristen walked up to five different elderly ladies and asked them for cookies. Kristen's behaviour illustrates the concept of

A) unconditioned reinforcement.
B) stimulus generalisation.
C) stimulus discrimination.
D) observational learning.