Option 3: (A) - (II), (B) - (I), (C) - (IV), (D) - (III) -> In economics, Marginal Propensity to Consume (MPC) measures the change in consumption for a unit change in income, expressed as ΔC/ΔY. Marginal Propensity to Save (MPS) measures the change in savings for a unit change in income, expressed as ΔS/ΔY. Average Propensity to Consume (APC) is the ratio of total consumption to total income (C/Y), while Average Propensity to Save (APS) is the ratio of total savings to total income (S/Y). Note that MPC + MPS = 1 and APC + APS = 1, as income is either consumed or saved. -> correct