In a singly linked list that uses a dummy head, how would you detect whether the list is empty?

• A. The head pointer is NULL.
• B. The first real node is NULL.
• C. The dummy head's next pointer is NULL.
• D. The tail pointer is NULL.

Answer: (C)

In a list with a dummy head, you always have a placeholder node at the front, and the real data starts after that node. The pointer you follow to reach the first data element is the dummy head’s next pointer. If there are no data elements, that next pointer is NULL. So checking whether the dummy head’s next pointer is NULL directly tells you the list is empty.

The head pointer itself points to the dummy node, so it would not be NULL even when the list has no elements. The “first real node” being NULL is effectively the same condition, but the standard check uses the dummy head’s next pointer. The tail pointer being NULL isn’t a reliable emptiness indicator in this setup, since its value depends on how you manage the tail and may not reflect emptiness consistently.