Why is average cost and short run marginal cost always u-shaped

The Marginal Cost curve is U shaped because at the beginning when a firm increases its output, average costs, as well as variable costs, start to increase at a diminishing rate. At this stage, due to economies of scale, Marginal Cost falls till it becomes minimum. Then as output rises, the marginal cost increases.

the answerr would be 1

answercompetitive advantage;