Best response to the King's Indian Defense: Fianchetto Variation, Yugoslav Variation, Rare Line (E64)

1. d4 Nf6 2. c4 g6 3. g3 Bg7 4. Bg2 O-O 5. Nc3 d6 6. Nf3 c5 · White to move

What is the best response to the King's Indian Defense: Fianchetto Variation, Yugoslav Variation, Rare Line (1. d4 Nf6 2. c4 g6 3. g3 Bg7 4. Bg2 O-O 5. Nc3 d6 6. Nf3 c5)? White to move. See the top replies ranked by opening theory and real-game results, starting with O-O.

The main theoretical reply is O-O, reaching the King's Indian Defense: Fianchetto Variation, Yugoslav Variation.