Natural monopolies occur when one producer

can meet the market's entire demand.

controls the method of production.

is the only one authorized to produce a given product.

creates unique products.

The correct answer is can meet the market’s entire demand.

Natural monopolies occur due to the fact that it is rather difficult to enter a business without proper gear and a company owner has money to invest in this. For example, McDonald's can't have a natural monopoly because it's relatively easy to enter the burger making business. On the other hand, oil companies often have natural monopolies because of everything that is necessary to enter the business.