After Being Bitten by a Dog, Jose Finds That He

After being bitten by a dog, Jose finds that he feels afraid whenever he sees a dog. He goes for treatment, where he is gradually exposed to dogs, until he can be in the same room with a dog without feeling any fear. Three weeks later, while walking in his neighborhood, Jose hears a dog barking viciously. For a few weeks after this, his fear returns. This shows ________

A) the treatment had no effect.
B) extinction.
C) stimulus-stimulus expectancy.
D) spontaneous recovery.