This is the most principled reply, ensuring that White can no longer get the open Sicilian.
1. e2e4  1... c7c5  2. g1f3  2... b8c6  3. b1c3 Shirov uses a well-known move order designed to avoid the infamous Sveshnikov Sicilian. This variation of the Sicilian is one of Gukesh's favorite weapons with the black pieces; his recent, brilliant win over Nodirbek Abdusattorov in Biel is the best example.