Final answer:
The monopoly in this scenario results from the ownership of scarce inputs, specifically the control of a physical resource that is essential for producing a product.
Step-by-step explanation:
The monopoly on land that contains the only known source of aloe for making anti-itch lotion results from ownership of scarce inputs. This type of barrier to entry occurs when a company controls a scarce physical resource. Historical examples, like ALCOA's control over bauxite, illustrate how such control can prevent other firms from competing effectively and establish a natural monopoly.