Which of the following is a fringe benefit excluded from income? 

a. A mechanic at Denise’s employer, a car rental company, provides $1,000 of repair services to Denise’s personal car for free. 

b. Alfa-Bet, a high-tech corporation, pays for each employee’s membership at the 24 Hour Biceps Gym closest to each Alfa-Bet office. 

c. Quickchat Inc. gives each employee a $10 giftcard to the local coffee shop on National Coffee Day. 

d. Hedaya, a doctoral student at Ivy University, receives a full tuition waiver while serving as research assistant.