I need to play in column 2 to block my opponent's diagonal threat. My opponent has X pieces at positions (3,1) and (3,4) that could connect with a piece in column 2 to form a diagonal win. By playing in column 2, I not only block this threat but also strengthen my horizontal position on the bottom row, where I'll have 4 connected O pieces (in columns 0, 1, 2, and 3).