Answer: d. A&C
Step-by-step explanation:
James Olds and Peter Milner´s discovery of reinforcement centers of the brain happened by accident in 1954.
They implanted an electrode inside a rat's brain, with the intention of stimulating the reticular system, when the rat, placed inside a box, approached a certain place. They expected the rat to eventually avoid that place.
However, the electrode curved off its expected course and landed near the hypothalamus, and the rat´s behavior indicated the brain stimulation was pleasurable.