I. Decide whether that sentence is true or false? 7. A pledge of property shall take effect as from the time at which the last party signs the document of pledge of property. 8. Invalid civil contracts will completely terminate legal liabilities between parties. 9. Contract for donation of property is a bilateral contract. 10. A contract that the effect of which does not depend on the auxiliary is a principal contract. 11. The pledge of a property may be cancelled, if so consented by the pledgee. 12. Disposal of mortgaged property is the same as disposal of security collateral property.