An Industry Is Said to Be a Natural Monopoly When

An industry is said to be a natural monopoly when

A) legal barriers limit entry into the market.
B) diseconomies of scale are present in the market.
C) the market demand for the product supplied by a firm is inelastic.
D) long-run ATC continues to decline as firm size increases.
E) larger firms have higher per-unit costs than their smaller rivals.