Explanation:

- Multiplier measures the effect of a change in investment or government spending on the overall economy.

- MPC (Marginal Propensity to Consume) indicates the portion of additional income that a consumer spends on goods and services.

- MPS (Marginal Propensity to Save) is the portion of additional income that is saved.

- Option 1: 1/MPC – Incorrect. This is not the formula for the multiplier.

- Option 2: 1/1-MPC – Correct. This is the commonly used formula for the multiplier in the Keynesian model.

- Option 3: 1/1+MPC – Incorrect. This formula misinterprets the multiplier.

- Option 4: 1/1+MPS – Incorrect. MPS complements MPC (MPC + MPS = 1).