Correct answer: Ra41...K:b2 2.Ra2# 1...Kd3 2.O-O-O# 1.Bb4?? zz 1...K:b2 2.Ra2# 1...Kd3 2.O-O-O# but 1...a5! 1.Nd4+?? 1...Kd3 2.O-O-O#/Rd1# but 1...