Dr. Richman is conducting research on whether women perform worse on a math test when they are asked to indicate their gender prior to taking the test. Dr. Richman is exploring the concept of .

Which of the following  bestillustrates a negative reinforcer?               a.  copland gives up candy to stave off chronic acid indigestion.    b.  nancy learns that she prefers chocolate over vanilla.    c.  carmine changes his major to english lit after failing a math exam.    d.  on a hot day, lindberg always drinks lemonade.