The basic objective of macroeconomics is to develop theoretical tools. They are called .........

Models.

The correct answer is Option (3) → Models.

The basic objective of macroeconomics is to develop theoretical tools, called models, capable of describing the processes which determine the values of these variables. Specifically, the models attempt to provide theoretical explanation to questions such as what causes periods of slow growth or recessions in the economy, or increment in the price level, or a rise in unemployment.