Step 1: Understanding the Concept:
Aggregate demand is a fundamental concept in Keynesian economics.
Step 2: Detailed Explanation:
According to Keynes, aggregate demand refers to the total demand for goods and services in an economy at a given time. It includes consumption, investment, government spending, and net exports:
\[
AD = C + I + G + (X - M)
\]
Among the given options, option (A) best represents this idea, as it refers to demand related to goods and services. The other options describe policies or effects, not the concept itself.
Step 3: Final Answer:
Goods and Services Sector