Final answer:
ALCOA used the barrier to entry known as control of a physical resource to try to establish a monopoly by controlling the majority of the world's supply of bauxite.
Step-by-step explanation:
ALCOA attempted to establish a monopoly by using the barrier to entry known as control of a physical resource. They controlled most of the world's supply of bauxite, a key mineral used in making aluminum. By controlling the supply of bauxite, other firms were unable to produce enough aluminum to compete with ALCOA.