The correct answer is (a) Interest on national debt.
Explanation
A transfer payment is a payment where the payer receives no current goods or services in return (its purpose is redistribution of income). Examples include government retirement/old‑age pensions and private donations — these move purchasing power without an exchange of goods or services.
- (b) Retirement pensions — transfer payments (government transfers to individuals).
- (c) Old‑age pensions — transfer payments (same as retirement pensions).
- (d) Donations — transfers of income/wealth without goods/services in return, so they are transfer payments.
Interest on the national debt is a return paid to holders of government bonds for lending their funds; it is payment for the use of capital (a reward to creditors) rather than a redistributive transfer, so it is not classified as a transfer payment.