When in an economy, available resources are fully utilized at that point production of a combination of goods is known as ..........

Production Possibility Frontier.

The correct answer is Option (3) → Production Possibility Frontier.

When an economy fully utilizes its available resources and technology, it produces combinations of goods that lie on the Production Possibility Frontier (PPF). The PPF represents the maximum possible output combinations of two goods that can be produced efficiently. Any point inside the curve indicates underutilization of resources, while points outside are unattainable with current resources and technology.