Option 1 -> National Income is a measure/concept in macroeconomics, not what theoretical tools are called.
Option 2 -> Components refer to parts or elements of something, not theoretical tools.
Option 3 -> Models are simplified representations used as theoretical tools in macroeconomics.
Option 4 -> Aggregate refers to total or combined measures like aggregate demand, not theoretical tools.
Hence, Option 3: Models -> In macroeconomics, theoretical tools are called models. These are simplified frameworks or representations of economic reality that help economists analyze relationships between variables like inflation, unemployment, GDP, etc. Examples include the IS-LM model, AD-AS model, and Solow growth model. These models allow economists to make predictions and understand complex economic phenomena. -> correct