Solution
Option 1 -> Refers to actual investment spending in the economy, not the concept where demand determines output.
Option 2 -> Refers to actual consumption spending, not the broader macroeconomic concept.
Option 3 -> The point where aggregate demand determines the level of output and employment in the economy.
Option 4 -> Does not represent the concept where demand determines output levels.
Hence, Effective demand -> This is a fundamental concept in Keynesian economics introduced by John Maynard Keynes. Effective demand represents the level of aggregate demand (consumption + investment + government spending + net exports) that actually determines the aggregate output and employment in an economy. Unlike classical economics which assumed supply creates its own demand, Keynes argued that in situations with unemployment and unused capacity, it is the level of effective demand that determines how much will be produced. When aggregate output is determined solely by aggregate demand, this point of intersection is called effective demand. -> correct