Answer:
2. An industry in which one firm can achieve economies of scale over the entire range of market supply.
Explanation:
A natural monopoly is an industry in which one single firm can obtain economies of scale over the entire range of market supply. As their cost of the product is higher, small scale producers can never fight with the larger producers. In this circumstance, the natural monopoly of an individual large producer has also the most efficient and cost-effective way to produce the goods.