Which type of bond is secured by property?

A mortgage bond is a type of bond that is explicitly secured by a specific piece of property or real estate. This collateral provides a guarantee to investors that in the event of default, they have a claim against the underlying property. This characteristic makes mortgage bonds less risky compared to unsecured bonds, as they provide a tangible asset that can be liquidated to recover the investment.

In the context of bonds, other options do not have this direct security backing. For instance, corporate bonds are issued by companies and can be backed by the company's overall creditworthiness but are not necessarily tied to specific assets. Debentures are a form of loan that is not secured by any specific asset and rely solely on the issuer's creditworthiness for repayment. Convertible bonds, while offering the option to convert into stock, also do not have property backing and are classified as unsecured debt.

Thus, the distinct characteristic of being secured by property makes a mortgage bond the correct answer to the question.