7. Which of the following statements is true and correct? a. Pledge and mortgage are accessory contracts because they cannot exist by themselves. b. In both pledge and mortgage, the creditor is entitled to deficiency judgment. c. Where an obligation is secured by a pledge or mortgage and it is not paid when due, the pledgee or mortgagee may dispose of the thing pledged or mortgaged if there is an agreement to that effect between the parties. d. Unless otherwise agreed upon by the parties, the sale of the mortgaged property extinguishes in full the obligation of the mortgagor to the mortgagee