If the​ firm's average cost curves are​ U-shaped, why does its average variable cost curve achieve its minimum at a lower level of output than the average total cost​ curve? The average variable cost curve will achieve its minimum at a lower level of output than the average total cost curve because A. average total cost equals average variable cost plus average fixed​ cost, and the average fixed cost curve continues to fall as more output is produced. B. average total cost equals average variable cost minus average fixed​ cost, and the average fixed cost of production reaches its minimum at a higher level of output than the average variable cost curve . C. average total cost equals average variable cost plus average fixed​ cost, and the average fixed cost of production is constant . D. average total cost equals average variable cost plus average fixed​ cost, and the decrease in average fixed costs with output is always smaller than eventual increases in average variable costs with output. E. average total cost equals average fixed cost plus marginal​ cost, and the marginal cost curve continues to fall as more output is produced.