Correct answer: B:f41...Kd1 2.Rg1# 1...d1B 2.Bb4# 1.Bb4?? zz 1...Kd1 2.Rg1# but 1...f3! 1.B:f4! zz 1...Kd1 2.Rg1# 1...d1Q/d1R 2.Bg
