Recall the definition of LinkedList from class. I've made a doubly linked list which is a child class of LinkedList. A doubly linked list has a first and last node and each node has a previous and a next pointer to other nodes. What is wrong with this function (it would be defined in DLinkedList. h but the error is in this function)? virtual void insertEnd(LLNode * toAdd)
{
LLNode * oldLast = getLastNode();

oldLast->setNext(toAdd);

p_last = toAdd;
toAdd->setPrev(oldLast);
}

Select one:
a. The previous pointer for the added node was not set.
b. oldLast may be NULL and can cause a NULL pointer exception.
c. insertEnd in LinkedList is a private function
d. If toAdd is NULL, "oldLast->setNext(toAdd);" causes a NULL pointer exception.