Samsa bought a new TV. At first, every time a phone rang on the TV, he got up to answer

his phone. However, within a couple of weeks this didn't happen any longer. He only
answered his own phone. This change in Samsa's behavior best illustrates

a. habituation.
b. stimulus generalization.
c. spontaneous recovery.
d. stimulus discrimination.
e. dissociative learning.

d. stimulus discrimination.