Explanation:

- Fiscal Deficit is the difference between the government's total expenditure and its total receipts (excluding borrowings).

- Primary Deficit is calculated by subtracting interest payments on previous debt from the fiscal deficit.

- Option 1: Defence expenditure - It is a part of total government expenditure but not used to calculate primary deficit.

- Option 2: Expenditure on subsidies - Another part of government spending but not relevant to primary deficit calculation.

- Option 3: Interest payments - These are subtracted from fiscal deficit to find the primary deficit.

- Option 4: Pension - Like subsidies and defense, not relevant to the primary deficit calculation.