Correct answer: Nb3*d4 1.Nb3*d4 ! danger: 2.Nd4*c2 # 2.Qf3-e2 # 1...a2-a1=N 2.Qf3-e2 # 1...b2-b1=Q 2.Qf3-e2 # 1...b2-b1=