I analyzed the board and noticed that our pieces already form a diagonal from (5,4) to (3,2). Adding a piece at (2,1) would complete a four‐in‐a‐row win. However, due to gravity, we can’t place directly at (2,1) because column 1’s next available cell is (3,1). By playing in column 1 now, we block any potential vertical threat from X (who already has two pieces in column 1) and set up our diagonal win: next time, if our opponent doesn’t block column 1, we can drop another O to land at (2,1) to win. Hence, the best move is to drop in column 1.