In 1977, two years after graduating from Yale Law School, Mr. Williams founded the firm Williams Legal Services with two other lawyers. By 2003, the company had expanded to 200 offices in twenty-two states. With growth, the company has found it easy to recruit staffers; however, it has faced other problems, most noticeably dissatisfaction among staff lawyers. Recently staffers in seven Minneapolis regional offices revolted, writing a memo protesting the firm's emphasis on generating fees at the expense of quality legal work. Mr. Williams fired the dissenters.
His action toward the dissenters indicates the use of:

a) positive reinforcement.
b) negative reinforcement.
c) extinction.
d) punishment.
e) collaboration.