The obligation secured by the insured mortgage under the loan policy is the:

The correct choice is indebtedness. In the context of a loan policy, the primary purpose of the policy is to protect the lender's financial interest in the event that there are issues with the title to the property. The amount of money that the borrower owes to the lender, which is the indebtedness, is what the mortgage secures.

The insured mortgage serves as a lien on the property, ensuring that the lender can recover the amount of the loan if the borrower defaults. This loan policy will cover the lender’s losses arising from defects in the title that could affect the enforceability of the mortgage, thus safeguarding the lender’s right to be repaid.

In contrast, while "policy subject" can reference the specifics or conditions of the policy, it is not the ultimate obligation that the mortgage secures. "Insurance liability" pertains to the scope of the title insurer's responsibility in the case of claims but does not define what obligation is secured by the mortgage itself. "Insured" refers to the party protected by the insurance policy but does not convey the concept of the economic obligation linked to the mortgage. Understanding these distinctions clarifies why indebtedness is the appropriate answer in this context.