Option 4: (A) - (III), (B) - (IV), (C) - (I), (D) - (II) -> This is the correct matching. (A) Marginal propensity to consume (MPC) is defined as the change in consumption divided by the change in income (ΔC/ΔY), which measures how much additional consumption occurs when income increases by one unit. (B) Consumption function is represented by the equation C = c + cY, where c is autonomous consumption and cY is induced consumption based on income. (C) Average propensity to consume (APC) is the ratio of total consumption to total income (C/Y), showing the proportion of income spent on consumption. (D) Aggregate Demand in a simple two-sector economy is the sum of consumption and investment expenditure (C + I). -> correct