(A) - (I), (B) - (III), (C) - (II), (D) - (IV) -> Let's match each concept: (A) Final goods market corresponds to (I) A + cY which represents aggregate demand in an economy where A is autonomous expenditure and cY is induced consumption based on income Y. (B) Consumers demand matches with (III) Ĉ + cY which is the consumption function where Ĉ is autonomous consumption and c is the marginal propensity to consume. (C) Investment multiplier corresponds to (II) ΔY/ΔA which shows the ratio of change in national income to change in autonomous expenditure, measuring the multiplier effect. (D) Linear equation matches with (IV) a + bX which is the standard form of a linear equation with 'a' as the intercept and 'b' as the slope coefficient. -> correct