Explanation:

- Deficient demand refers to a situation where the total demand for goods and services in an economy is less than its total supply. This occurs when consumer spending and business investments are lower than what the economy can produce.

- Option 1: Deflationary Gap

- This is the correct option.

- A deflationary gap happens when actual output is less than potential output, leading to unemployment and unused capacity.

- It results from deficient demand, where aggregate demand is insufficient to reach full employment output.

- Option 2: Inflationary Gap

- An inflationary gap arises when aggregate demand exceeds an economy’s potential output.

- This typically leads to rising prices and inflation, not caused by deficient demand.

- Option 3: Both (a) and (b)

- Incorrect as both scenarios can't simultaneously result from deficient demand.

- Option 4: None of these

- Incorrect given the defined situation.