Correct answer: Nd51...f3 2.Bd6# 1.a5?? (2.Qe7#) but 1...Kb4! 1.Ne4+?? 1...Kd5 2.Qe5# but 1...Kb4! 1.Qa7+?? 1...Kd6 2.Qe7# but 1...Kb4! 1
