Correct answer: Rg41. Rg4! waiting 1. ... N:a7 2. Q:b7# 1. ... Ne7 2. Nd6, Q:b7# 1. ... Nb6/d6 2. N(:)d6# 1. ... b6 2. Qc6# 1. ... Ra4 2. Q:a4# 1. ... Qg