Which of the Following Best Illustrates the Process of Positive

Which of the following best illustrates the process of positive reinforcement?

A) A child is sent to her room after screaming while at the dinner table.
B) A hungry rat presses a lever to obtain a food pellet.
C) A rat presses a lever that results in delivery of shock through the floor of the chamber.
D) A woman injects heroin into her veins to obtain a "rush."
E) A man ingests an aspirin to rid himself of a strong headache.