Originally posted by Ragnorak
white's last move, not black.
Nobody ever gave -1...Kg1xNh2 as black's last move. If his last move was only -1...Kg1-h2, there is nothing on h2!
Furthermore, after the forced -1...Kg1xNh2, White's previous move could be either -2.Nf1-h2 without capture, or -2.Nf1xh2 uncapturing a black Queen, Knight or Rook on h2. That's why the stip only asks for black's last move.