Answer:
The answer is D. They respond at least as well as when they are rewarded on every trial.
Explanation:
Intermittent reinforcement is when the reward is only provided only part of the time, it is usefull once the response is firmly established. To establish the response, it is recommended that the reward is given every time the behavior occurs, but once the conection has been made, intermittent reinforcements prevent extinction of the behavior; since it is unrealistic that the reinforcement is given every single time, it has been proved that intermittent reinforcement produce the same response as when the reward is given on every trial.
