This is a position from the game Gaprindashvili vs Khuberashvili, Moscow, 1959. The answer is very easy for the question ‘What’s White’s winning shot?”

Gaprindashvili vs Khuberashvili

Result: 1-0
Site: Moscow
Date: 1959
[…] 1.♗e7+ The Black King has nowhere to go and has to move the Knight protecting the Rook on a7 1…♘xe7 2.♖xa7