When Using the Textbook's Implementation of a Singly Linked List

When using the textbook's implementation of a singly linked list to remove an element in the middle of the list, why it is necessary to check whether the previous reference equals the position reference?

A) If previous equals position, the action does not follow a call to next.
B) If previous equals position and an attempt is made to remove the node, the iterator would have to start at the beginning of the list to rebuild the links.
C) If previous equals position, the iterator is at the beginning of the list and does not point to a valid node.
D) If previous equals position, the iterator is at the end of the list and does not point to a valid node.