Which of the Following Is Untrue

Which of the following is untrue?

A) It is generally assumed that total variable costs increase when sales increase.
B) It is generally assumed that fixed cost per unit remains the same when sales decrease.
C) It is generally assumed that total monthly fixed cost remains the same as the volume of sales changes from the busy to the quiet season in a year.
D) It is generally assumed that variable costs remain approximately the same per unit sold as the volume of sales changes from the busy to the quiet season in a year.
E) Many overheads are fixed costs.