If There Are Economies of Scale Throughout the Relevant Output

If there are economies of scale throughout the relevant output range of production, which is false?

A) It is a natural monopoly.
B) It is more efficient to have a single firm produce the good.
C) It would typically result from a firm's possession of an exclusive patent.
D) One large firm can produce at lower cost than two or more smaller firms.
E) None of the above is false; all are true.