Correct answer: f51. f5! waiting 1. ... g:h5+ 2. K:h5# 1. ... g:f5+ 2. K:f5# 1. ... B:g5 2. K:g5# 1. ... R:a3 2. b:a3# 1. ... Rb4 2. Kg3/h3/f3, b3# 1. ... R:b5 2. b4# 1. ... R<