The set of all possible combinations of the two inputs, labour and capital, that yield the same maximum possible level of output is called...........

Option 1: Indifference Curves -> These represent combinations of two goods that provide a consumer with the same level of satisfaction or utility, used in consumer theory.

Option 2: Isocost curve -> This shows all combinations of inputs (labor and capital) that can be purchased for the same total cost.

Option 3: Production Possibility Set -> This represents the set of all feasible input or output combinations available to a firm given technological constraints.

Option 4: Isoquant -> This shows all combinations of inputs that produce the same level of output.

Hence, Option 4: Isoquant -> An isoquant (meaning 'equal quantity') is a curve that represents all possible combinations of two inputs, typically labor and capital, that yield the same maximum level of output. It is analogous to an indifference curve in consumer theory, but applies to production. For example, a firm might produce 100 units using either 10 workers and 5 machines, or 5 workers and 10 machines - both combinations would lie on the same isoquant. The shape of isoquants reflects the substitutability between inputs in the production process -> correct