Mamedyarov chooses a line that was tested by Topalov in both his WCC matches against Kramnik and Anand—and which was also often a choice of Carlsen himself.
1. d2d4  1... g8f6  2. g1f3  2... d7d5  3. c2c4  3... e7e6  4. g2g3 Carlsen keeps milking his amazing Catalan WCC preparation. 4... d5c4  5. f1g2 