Correct answer: Kd11...Ng3/Nd2 2.N:g3# 1...N:h2 2.O-O-O# 1.Ra2?? zz 1...Ng3/Nd2 2.N:g3# but 1...N:h2! 1.Ra3?? zz 1...Ng3/Nd2 2.N:g3#
