I'm choosing column 5 because my opponent already has two X pieces stacked vertically there (at positions (4,5) and (5,5)). If I don't block this column now, they could place their next piece at (3,5), creating a vertical line of three Xs, which would force me to block at (2,5) in my next move or risk losing. By playing at (3,5) now, I'm proactively preventing this threat. Additionally, this move creates a diagonal connection with my piece at (4,4), which could potentially be developed into a winning strategy in later moves.