Option 1: (A) - (IV), (B) - (III), (C) - (II), (D) - (I) -> Let's match each concept: (A) Effective demand refers to the aggregate demand at the equilibrium level where AD = AS, matching with (IV). (B) Say's law of markets is the classical principle stating that supply creates its own demand, matching with (III). (C) Inflationary gap occurs when aggregate demand exceeds aggregate supply at full employment, causing price inflation, matching with (II). (D) Aggregate supply represents the total output of an economy, which equals National Income in economic accounting, matching with (I). -> correct