What are the differences between secured and unsecured debentures? Select one: a. A secured debenture is a contract for a debenture that has been put in writing. b. An unsecured debenture holder is one whose security is not registered against land. c. A secured debenture is one that is secured against property, in other words there is a registered security, which can be taken, if the debenture is not paid. d. Unsecured debentures describe any debts held against a company, which have not been put into writing