Option 1 -> This describes excess demand or inflationary gap, not deficient demand.
Option 2 -> Too broad; deficient demand specifically relates to full employment level, not any level.
Option 3 -> This describes excess demand situation, opposite of deficient demand.
Option 4 -> This correctly defines deficient demand where AD falls short at full employment.
Hence, Option 4: Aggregate demand falls short of aggregate supply at full employment -> Deficient demand (or deflationary gap) occurs when the total demand in an economy is insufficient to purchase all goods and services that could be produced at full employment level. This leads to underutilization of resources, unemployment, and downward pressure on prices. The economy operates below its potential output, creating a gap between what could be produced and what is actually being demanded at full employment-> correct