An interesting side line, which the world  champion used last year too.
1. e2e4  1... c7c5  2. g1f3  2... d7d6  3. d2d4  3... c5d4  4. f3d4  4... g8f6  5. b1c3  5... g7g6  6. c1e3  6... f8g7  7. f2f3  7... a7a6  8. d1d2  8... h7h5  9. f1c4  9... b8d7 Carlsen prefers to develop first before pushing the b-pawn. 10. e1c1  10... b7b5  11. c4b3 