Correct answer: Rd51...b:a3 2.O-O# 1.Bb1?? (2.Rd1#) but 1...K:b1! 1.f3?? zz 1...b:a3 2.Kf2#/O-O# but 1...e:f3! 1.f4?? zz 1...b:a3 2.Kf2#/O-O# but 1...e:f3 e.p.! 1.Kf1?? zz
