What does the back() function do in a linked list?

• A. It returns a reference to the data in the tail node, with the precondition that the list is not empty
• B. It returns the tail pointer
• C. It removes the tail node
• D. It returns a copy of the head data

Answer: (A)

The back function provides access to the value stored in the last element of the list. It typically returns a reference to the data in the tail node, and you must ensure the list is not empty before calling it. Because it returns a reference, you can read or modify the last element in place without making a copy. It does not remove the last node—that’s a separate operation like pop_back or remove. It also doesn’t return the tail pointer itself; that would be a different function if your API exposes the node or its address. And it isn’t returning a copy of the head data—that would be front or a similar function for the first element.