A good, useful move against Black's b5-b4 advance. Castling immediately is also possible.
1. e2e4  1... e7e6  2. d2d4  2... d7d5  3. b1c3  3... g8f6  4. e4e5  4... f6d7  5. f2f4  5... c7c5  6. g1f3  6... b8c6  7. c1e3  7... f8e7  8. d1d2  8... a7a6  9. d4c5 Anand releases the central tension immediately. Carlsen chose another move in a recent game. 9... d7c5 