The correct answer is Option (3) → (B), (A), (D), (C)
Note: The given answer is per NTA answer sheet. But this appears to be wrong and not as per NCERT. The correct should have been Option 1: (B), (A), (C), (D) as explained below:
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(B) Equilibrium level of income depends on aggregate demand. This is a foundational statement setting the context that changes in aggregate demand will affect income.
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(A) When autonomous investment increases, the aggregate demand shifts in parallel upwards. This describes the initial shock or change in aggregate demand. Autonomous investment is a component of aggregate demand, and an increase in it shifts the aggregate demand curve up.
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(C) Excess demand emerges in the economy. When aggregate demand shifts upwards, at the original equilibrium income level, the new (higher) aggregate demand exceeds the current output (aggregate supply). This creates a situation of excess demand.
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(D) The output will be greater than the original output. In response to the excess demand, firms will increase production, leading to a new, higher equilibrium level of income and output. This also implies the multiplier effect where the final increase in output is greater than the initial autonomous investment increase.

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