Which of the following statements about object oriented databse is not correct?

Which of the following statements about object oriented databse is not correct?

A． Each object has a unique object identity in the system.

B．Encapsulation and inheritance are two important features of object oriented databasE.

C．A subclass can inherit the attributes and methods of all its superclasses.

D．A subclass includes the attributes and methods of all its subclasses.