Correct answer: Nf31...f4 2.Ng4# 1...Ng6/Ng8/Nc6/Nc8 2.N:d5# 1.Bc6?? zz 1...Ng6/Ng8/N:c6/Nc8 2.N:d5# 1...f4 2.Ng4# but 1...b5! 1.B