Which of the following terms refers to a mortgage that covers more than one piece of real estate?

A blanket mortgage is specifically designed to cover multiple properties under a single loan agreement. This financial instrument allows borrowers to finance several pieces of real estate, such as multiple lots, homes, or parcels of land, with a single mortgage instead of needing separate loans for each property. This can be advantageous for developers or real estate investors who wish to streamline their financing process and reduce the complications associated with managing numerous loans.

Conventional mortgages typically refer to loans that are not backed by government programs and are usually secured by a single property, so they wouldn't cover multiple parcels. Open mortgages allow borrowers to pay off the mortgage without incurring penalties, but they are not related to multiple properties. A purchase money mortgage is used to finance the acquisition of property and similarly pertains to a single transaction rather than covering more than one piece of real estate. Thus, the blanket mortgage stands out as the correct answer in the context of real estate financing.