When Jay Is Playing the Guitar Piece Correctly, Jay Sees

Multiple Choice

When Jay is playing the guitar piece correctly, Jay sees his teacher smiling and nodding his head in time to the music. If Jay increases his behavior because of this smiling and nodding, one can say that the smiling and nodding served as a(n) :

A) positive reinforcement.
B) negative reinforcement.
C) positive punishment
D) unconditioned stimulus.