White can achieve a draw in this position by promoting the pawn to a knight (with check) and taking the Black queen on his next turn. While the knight can eventually capture all three Black pawns, it is not capable of checkmate on its own. Any good computer will demonstrate that promoting the pawn to a queen loses against best play. Stockfish even begins by setting a little trap: 1. c8=Q Qg7 and if 2. Kxb4 Qb2 checkmate (see the diagram below).
White can achieve a draw in this position by promoting the pawn to a knight (with check) and taking the Black queen on his next turn. While the knight can eventually capture all three Black pawns, it is not capable of checkmate on its own. Any good computer will demonstrate that promoting the pawn to a queen loses against best play. Stockfish even begins by setting a little trap: 1. c8=Q Qg7 and if 2. Kxb4 Qb2 checkmate (see the diagram below).