Correct answer: Bd71. Bd7! [2. Nf3 3. Be7#] 1. ... a5 2. Nf3 a:b4 3. Be7# 1. ... Ke5 2. Nf3+ Kf4 3. Bg5# 1. ... Nf4 2. Be7+ Ke5 3. Nf3#
