Answer:
a. a surety.
Explanation:
-A surety is a person that is primarely liable to pay an obligation that another person has.
-A lienor is someone that owes money and because of that the property he/she owns is kept by the lender until the full amount is paid back.
-A guarantor is a person that takes the responsability to pay an obligation of another person if he/she doesn't make the payments. However, the lender has to take all the measures against the principal debtor in the loan before going against the guarantor.
-A creditor is a person or organization that lends money to be repaid in the future.
According to the meaning of the options given, Harper is a surety.