Regarding the Experiments Using Intracranial Self-Stimulation (ICS) of the Pleasure

Regarding the experiments using intracranial self-stimulation (ICS) of the pleasure centers, which of the following statements is FALSE?

A) When rats self-administer nicotine, they are even more likely to engage in ICS because nicotine further increases the sensitivity of the pleasure pathways.
B) After the rats had pressed the ICS lever to exhaustion, they were less likely to press the lever again once they were revived.
C) Humans who have had direct brain stimulation report feeling intense pleasure that is better than food, water, sex, or drugs.
D) Intracranial self-stimulation (ICS) is considered to be a primary reinforcer.