Choose the correct description for the following sudoku solving technique: Hidden Pair

A) A 3x3 variant of X-Wing where three rows align with three columns, allowing eliminations outside intersections.

B) Within a row, column, or box, if a digit can go in only one cell, that cell must contain it, even if other candidates exist.

C) Four digits that each appear in only four cells of a house restrict those cells to those digits.

D) Two digits that each appear in exactly the same two cells of a house restrict those cells to just those digits.
