Correct answer: Kf21...Kc2 2.Be4# 1...Nd2 2.R:c3# 1...N:a3 2.O-O-O# 1.N:b6?? zz 1...Nd2 2.R:c3# 1...N:a3 2.O-O-O# but 1...Kc2! 1.R1:a2?? zz 1.