Correct answer: Kf11...Kb1 2.O-O# 1...d:e2 2.K:e2# 1.Qc3+?? 1...Kb1 2.O-O# but 1...b:c3! 1.N:b3+?? 1...Kb1 2.B:d3# but 1...Kc2! 1.Rg1?? zz 1...d:e2 2.<
