When marginal cost is rising:

A) average variable cost must be rising.
B) average total cost must be rising.
C) average variable cost and average total cost must be falling.
D) both average variable cost and average total cost may be rising or falling.

Marginal Cost

The additional cost incurred by producing one more unit of a product, which can vary depending on the level of production.

Average Variable Cost

The variable cost of production divided by the quantity produced, showing the cost of producing each additional unit.

Average Total Cost

The total cost of production divided by the number of units produced, representing the per-unit cost of production for a firm.