Which of the Following Loops Correctly Uses Iter as an Iterator

Multiple Choice

Which of the following loops correctly uses iter as an iterator to move through the nodes of the linked list?
NodePtr iter; //a pointer to a node

A) whileiter != NULL) iter++;
B) whileiter != NULL) iter=iter->link;
C) foriter=NULL; iter != NULL; iter=iter->link)
D) for iter=head; iter != NULL; iter=iter->link)