Answer:
His behavior demonstrates negative reinforcement in operant conditioning.
Explanation:
In operant conditioning, there are reinforcements and punishments and they can be positive or negative.
Negative reinforcement refers to the removal of a generally aversive stimulus in order to reinforce a certain conduct.
In this case, Liam is disturbed by the loud music (an aversive stimulus) so in order for him to continue his studying undisturbed, he removes the stimulus by closing the window.