Playing in column 4 is optimal for multiple reasons:

1. It blocks a potential vertical threat - my opponent already has two X pieces in column 4 and could build toward a vertical four.

2. It creates a horizontal line of three O pieces at row 2, connecting with my existing O pieces at (2,2) and (3,2), setting up a potential horizontal win.

3. It also creates a diagonal line of three O pieces, connecting with my O pieces at (3,1) and (2,0), setting up a potential diagonal win.

4. This move creates multiple threats simultaneously, forcing my opponent to defend in multiple directions on their next turn.