Which Promotion Exemplifies the Use of a Fixed-Ratio Schedule of Reinforcement

Which promotion exemplifies the use of a fixed-ratio schedule of reinforcement?

A) A café prints "You are a winner" on a random one-twelfth of its coffee lids; patrons receiving such a lid can redeem it for a free beverage.
B) A café offers its customers a punch card.Each time the patron purchases a beverage,a hole is punched; when ten holes have been punched,he or she receives a free beverage.
C) Every now and then,a café announces a two-for-one deal.
D) A café offers a two-for-one deal from 5 a.m.to 6 a.m.on Monday mornings.