> Not necessarily. It could be "B", if player one goes A, player
> two goes G, and then player one chooses C.

> ~Kinescope

Right, but the letters are presented in a particular order: "ACG". It would make sense for that to be the order of the moves in the game, with players one (marked in red) and two (green) alternating moves. D is the only response that would make sense for player two. The best next move for the first player is space I. This seals the win because the second player can't block both the bottom row and the upper-left to lower-right diagonal at the same time (spaces E and H). I'm pretty sure that there is no better set of moves for either player given this layout.

Here's the board again, for reference.

A	B	C
D	E	F
G	H	I