Consider the following statements when answering this questionI. Whenever a firm's average variable costs are falling as output rises, marginal costs must be falling too.II. Whenever a firm's average total costs are rising as output rises, average variable costs must be rising too.
A. A. I is true, and II is false. B. B. I is false, and II is true C. C. I and II are both true. D. D. I and II are both false.