Which of the following encumbrances would constitute a lien on real property?

A mortgage constitutes a lien on real property because it represents a legal claim that a lender has against a property as security for the repayment of a loan. When a property owner borrows money to purchase or refinance a home, a mortgage is created. This means that the lender has the right to pursue the property in case the borrower defaults on the loan. The mortgage effectively encumbers the property, ensuring that the lender's interest is protected throughout the repayment period.

In contrast, a lease agreement grants a tenant the right to occupy and use the property, but it does not create a lien; instead, it gives the tenant a possessory interest. A property tax assessment is a different type of encumbrance; while it can lead to a lien if taxes are not paid, the assessment itself is not a lien but rather a determination of the value of property for taxation purposes. A purchase contract is an agreement between buyer and seller for the sale of property, which does not create a lien but instead outlines terms related to the transfer of ownership.