Concept: An irredeemable bond is a perpetual bond that pays interest indefinitely without repaying the principal.Explanation: An irredeemable bond has no maturity date. It gives the holder a fixed interest payment each year but the issuer never returns the original capital. A development bond and long‑term loan eventually repay the capital. A redeemable bond is repaid at its maturity date. Therefore, only an irredeemable bond leaves the capital unpaid.Answer: C. an irredeemable bond