19. A linked list is represented by a reference to (4 points) A) the first node in the list, unless the list is empty, in which case the B) to the list representation object, which contains a boolean flag C) the superclass of the list D) None of the above set to false when the list is empty 20. In Java, the first node in a list has index (4 points) A)-1 B)0 C) 1 D) 2 e class for a linked list that can hold elements of type Object can be declared to have fields (4 points) A) Object element; B) Object element; Node next; C) Object element; Node next; D) Object element; next element; 22. In a linked list, the predecessor of a node x (4 points) A) is undefined if X is the first node, otherwise it is the node whose index is one less than the index of X B) is the first node in the list C) is the node that comes after X D) is the node that is just before X 23. The objects that form the units of memory allocation in a linked lists are called (4 points) A) memory modules B) elements C) nodes D) links 24. In a linked list, the successor of a node X (4 points) A) may not exist B) is the node that comes after X, and it always exists C) is the last node in the list D) is the node whose index is one greater than the index of xX