A knight blocking a pawn on its promotion square is attacked by the enemy king; it survives only by jumping to a square from which it still controls the promotion square.
The knight sits on e1, the pawn's promotion square, and the black king on d2 attacks it. White has to move the knight and must still cover e1 afterwards. Which squares attack e1? c2, d3, f3, g2. Of those, c2 and d3 are adjacent to the black king and would be captured; f3 gives check and is safe; g2 is safe and also covers e1.