A resident decedent was married under the conjugal partnership of gains. An obligation of P100,000, incurred during the marriage and secured by a mortgage of exclusive property is:

a. A deduction from the gross estate at P100,000 against conjugal property.

b. A deduction from the gross estate at P100,000 against exclusive property.

c. A deduction of P50,00 from the gross estate against conjugal property.

d. A deduction of P100,00 from the gross estate against exclusive property, but with a receivable of P50,000 from the surviving spouse.