Could you help me in solving this question, Doctor, as soon as possible, please, and thank you.

Which of the following statements about CVP analysis is true? O a. Operating income calculations in CVP analysis are based on gross margin. O b. The CVP analysis assumes that total variable costs remain the same over a relevant range. O c. . All of the given answers are false. O. d. Unit selling price, unit variable costs, and total fixed costs are known and remain constant