If two singly linked lists intersect by reference, what can be inferred about their tails?

• A. They share the same tail node
• B. They must have equal lengths
• C. They cannot share nodes
• D. Tail pointers are always null

Answer: (A)

When two singly linked lists intersect by reference, they actually merge into one sequence of nodes from the point of intersection onward. From that point to the end, both lists share the exact same nodes, so they end at the same last node. That means their tails are the same node. The paths from each head to the intersection can be different lengths, so equal lengths aren’t required. It’s not true that they can’t share nodes, since the shared tail confirms they do. And the tail isn’t necessarily null here; the last node exists and is common to both lists.