Which of the following transportation-related costs paid by an employer to or on behalf of an employee cannot be excluded from gross income?

a. Providing bus passes to employees for a $20 discount.

b. Paying for the parking of only senior executives at a cost of $250 per month.

c. Paying the occasional ride-sharing fare for an employee that has worked overtime late into the evening.

d. Paying $10 per month for bicycle storage for employees that bike to work.