What Is a "Natural" Monopoly

What is a "natural" monopoly?

A) One that occurs without any business firm trying to achieve it,i.e.,it just happens because the business does things right
B) A situation where one company can most efficiently supply all the product or service that is needed by consumers
C) One where government finds it "natural" to grant monopoly powers to certain business firms such as consumer products companies
D) One that occurs when a business firm sets out to achieve a monopoly and no other firm tries to stop it
E) There is no such thing as a natural monopoly.