Nurses on a unit met with the nurse manager as part of participatory budgeting.

Nurses on a unit met with the nurse manager as part of participatory budgeting.They ask,“What exactly is the difference between fixed and variable costs? Understanding this will helpus better understand the budgeting process.” The manager provides a definition and asks thestaff to list types of direct and indirect cost. Which example would indicate a need for further teaching?
a.
Fixed costs would include accreditation fees.
b.
Fixed cost would include the cost for the automated medication-dispensing system.
c.
Variable cost would include the nurse manager’s salary.
d.
Variable cost would include the salary expense for registered nurses.

The answers is supposedly D, but why is it not C?