Which statement correctly describes inserting at the tail when a tail pointer is available?

• A. Tail.next = new; tail = new; new.next = null.
• B. New node is inserted by updating head.
• C. Tail.next = new; new.next = tail; tail = new.
• D. Tail = new; tail.next = null; new.next = null.

Answer: (A)

When you have a tail pointer, appending at the end is done by linking the current last node to the new node, moving the tail pointer to the new node, and making the new node’s next reference null. This keeps the list properly terminated and allows the end to be reached in O(1) time.

The sequence shown implements exactly that: it sets the current tail’s next to the new node, then updates the tail to refer to this new node, and finally sets the new node’s next to null to mark the end of the list. This preserves the correct linkage from old tail to new node and ensures the list ends correctly.

Other patterns fail for reasons like not linking from the existing tail to the new node, introducing a backward link to the old tail, or misplacing the tail update so the new node isn’t properly integrated as the last element.