The average total cost curve and the average variable cost curve get A. farther and farther apart as output increases, because the marginal cost curve is declining. B. farther and farther apart as output increases, because the average variable cost curve is rising. C. closer and closer as output increases, because the average fixed cost curve is declining. D. closer and closer as output increases, because the marginal cost curve is rising. E. closer and closer as output increases, because the average variable cost curve is rising