Debtor Owes Creditor ₱500,000

Debtor owes Creditor ₱500,000. The debt is secured by a chattel mortgage on Debtor's car. On the due date of the obligation, Creditor is paid by Third Person who has no interest in the obligation either as guarantor or surety. There is likewise no stipulation as to Third Person's right to pay.

A) If Third Person pays without the knowledge or against the will of Debtor, Third Person may recover ₱500, 000 from Debtor even if the debt had been condoned to the extent of ½.
B) If Third Person pays with the Debtor's knowledge and consent, Third Person may recover ₱500, 000 from Debtor even if the debt had been condoned to the extent of ½. If Debtor fails to pay, Third Person may foreclose the mortgage on Debtor's car.
C) Same as letter "b" except that Third Person may not foreclose the mortgage on Debtor's car, unless Creditor consents.
D) Same as letter "b" except that Third Person may not foreclose the mortgage on Debtor's car because the mortgage was exclusively constituted in Creditor's favor.