The guarantor paid the obligation of the debtor when demand is made. Can he ask for reimbursement?

• A. No, because he is a voluntary payor;
• B. No, because judgment has yet to be obtained against the debtor;
• C. No, because he has not been able to exercise the benefit of excussion;
• D. Yes, because the benefit of excussion is a right granted to him which can be waived.