Correct answer: Kf21...Kd3 2.O-O-O# 1...Kb3 2.Bd1# 1.N:f4?? (2.Bd1#) but 1...g:f4! 1.Kf1?? zz 1...Kb3 2.Bd1# but 1...Kd3! 1.Be2?? zz 1...Kb3 2
