Which of the following is defined in the Transfer of Property Act, 1882 as a security for repayment of…

Section 58(a) of the Transfer of Property Act, 1882 defines a mortgage as the transfer of an interest in specific immovable property for the purpose of securing the payment of money advanced by way of loan, an existing or future debt, or the performance of an engagement. So the transfer defined as a security for repayment of a loan is a "Mortgage". An exchange (section 118) is a mutual transfer of ownership, and a lease (section 105) transfers a right to enjoy property for a price; neither secures a loan.