Which of the Following Accurately Describes a Debenture

Which of the following accurately describes a debenture?

A) A legal contract between the bond issuer and the bondholders.
B) A type of bond issued in the names and addresses of the bondholders.
C) A type of bond which requires the bond issuer to create a sinking fund of assets set aside at specified amounts and dates to repay the bonds.
D) A type of bond which is not collateralized but backed only by the issuer's general credit standing.
E) A type of bond that can be exchanged for a fixed number of shares of the issuing corporation's ordinary shares.