Which of the Following Is NOT an Assumption of Cost-Volume-Profit

Which of the following is NOT an assumption of cost-volume-profit (CVP) analysis?

A) The only factor that affects total costs is a change in volume, which increases or decreases total variable and mixed costs.
B) The price per unit does not change as volume changes.
C) Total fixed costs do not change.
D) The price per unit changes as volume changes.