Explanation:

- Option 1: Less than full employment

- Keynes argued that equilibrium could occur at less than full employment due to insufficient aggregate demand.

- Referred to as an underemployment equilibrium, where resources are not fully utilized.

- Option 2: Full employment

- Keynes acknowledged this as a classical economic idea where AD equals AS at full resource utilization.

- However, he believed economies often fall short of this point.

- Option 3: Beyond full employment

- This situation can arise temporarily with excess demand, leading to inflation.

- It is unsustainable but theoretically possible in Keynesian economics.

- Option 4: All of these

- Equilibrium can theoretically occur in all these states, as equilibrium concerns balanced AD and AS, not resource utilization level.

Option:4- All of these