Researchers have identified the gene that controls the development of the dopamine type D2 receptor in humans. People with the less common form of this gene were:

    a.    frequently introverts.
    b.    somewhat less likely than others to develop severe alcoholism.
    *c.    somewhat more likely than others to engage in a variety of pleasure-seeking behaviors.
    d.    somewhat less likely than others to engage in a variety of pleasure-seeking behaviors.