? Black will be unable to support the c pawn now.

! This is why black should have played ... Qe7/Qe6 earlier. With the B on c6 unsupported, white now gets tactical tricks.

! I think white's e pawn is stronger than black's c pawn. Black's advantage is gone.

Exchanging pieces now favors white, since the resulting endgame should be winnable.

Of course black is not so obliging as to trade queens!

Finally forcing the Q exchange.

Of course not 38 ... a5 39.Rb1 wins.

White's plan is to contain black's Q-side pawns by forcing the a pawn to a4, with the rook *behind* the pawns to prevent the b4 push. If black's king comes over, white goes after the K-side pawns. If black's K stays on the K-side, white will sac. the rook for the Bishop + Q-side pawns, and the outside passer on the a file should be enough to win.

First part of the plan is complete.

This move is forced, and is the reason white's plan has a chance of succeeding. White will march his K to c3, and if black's king stays away, white will play Rxc4 and clean up the black Q-side pawns.