I'm choosing column 6 because it builds on my existing O at position (6,5), giving me two Os in a vertical line. While this doesn't create an immediate win, it's a strategic placement that may set up future winning opportunities. My opponent has three Xs in a row at (3,2), (4,2), and (5,2), but they can't immediately play at (6,2) to win because pieces must stack from the bottom - they would need to fill (6,3) and (6,4) first. By playing at column 6, I'm developing my position while not enabling any immediate threats.