Which of the Following Promotions Exemplifies the Use of a Fixed-Ratio

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

A) A café prints "You are a winner" on one-twelfth of its coffee lids. Patrons who receive such lids can redeem them for free beverages.
B) A café provides its customers with punch cards. Each time a patron purchases a beverage, a hole is punched, and when ten such holes are punched, the patron receives a free beverage.
C) A café offers each patron an early morning two-for-one free-beverage-with-purchase deal from 5 to 6 a.m. on Monday mornings.
D) Occasionally, a café announces a two-for-one deal.