Juan easily taught his cat to jump through a hoop for the reward of food, but could not get his cat to fetch a ball and return the ball to him. The cat would chase the ball but use his paws to roll the ball so he could chase the ball again. The reason the cat had difficulties with fetching the ball was because of:
instinctive drift.

Instinctive drift

Explanation:

Instinctive drift is a phenomenon that occurs when an animal reverts back to instinctual behaviour, instead of continuing engaing in learned, or trained behaviour.

In this case, the cat's trained behaviour is being hampered by instinctive drift because while it can easily follow Juan's instructions when jumping a food (aided by the great incentive of getting food), it cannot help chasing the ball more than once, because rolling a ball to catch it is a highly instinctual behaviour that the cat practically cannot control.

answer; ///i do believe that the correct answer is ; /// (d)/return to polytheistic

it is due to the halo effect as the impression of the boy created earlier.on the mind of the principle affected his decision