The correct option is D If the creditor releases the principal debtor, or acts or makes an omission which results in the discharge of the principal debtor
Section 139 of the Indian Contract Law states "Discharge of surety by creditor’s act or omission impairing surety’s eventual remedy.—If the creditor does any act which is inconsistent with the rights of the surety, or omits to do any act which his duty to the surety requires him to do, and the eventual remedy of the surety himself against the principal debtor is thereby impaired, the surety is discharged."