I'm choosing column 4 for two strategic reasons. First, it blocks a potential diagonal threat from my opponent who has X pieces at (2,5) and (3,4) - if they were to play at (4,3), they would have a strong diagonal threat. Second, I already have two O pieces in column 4, so placing a third one helps build toward a potential vertical connect-four for myself. This move both defends against a threat and advances my position without creating any obvious advantage for my opponent.