When reversing a block of k nodes in a singly linked list, what happens to the order of nodes within that block?

• A. The order of nodes within the block remains the same.
• B. The order of nodes inside the block is reversed.
• C. The block is moved to the end of the list.
• D. The direction of traversal is inverted globally.

Answer: (B)

Reversing a block of k consecutive nodes in a singly linked list rearranges the next pointers inside that block so the order of those k nodes becomes the opposite of what it was. The first node in the block ends up last, and the last node ends up first, while the connections to the rest of the list stay the same at the block’s ends. For example, A -> B -> C -> D, reversing the first three nodes yields C -> B -> A -> D. The rest of the list is untouched except that it now connects to the new ends of the reversed block.