If a firm's average variable cost curve is rising, its marginal cost curve must be

Answer: Option C

If a firm's average variable cost curve is rising, its marginal cost curve must be above the average variable cost curve. If average costs are falling then marginal costs must be less than average while if average costs are rising then marginal must be more than average. Marginal cost on its way up must cut the cost curve at its minimum point. If Marginal Cost is less than Average Variable Cost, then Average Cost goes down.