Which of the Following Is True

Which of the following is true?

A) It is generally assumed that variable costs become greater per unit as sales increase.
B) It is generally assumed that variable costs become less per unit as sales decrease.
C) It is generally assumed that total variable costs are unaffected by a reduction in sales.
D) It is generally assumed that variable costs remain approximately the same per unit, regardless of the volume of sales
E) None of the above