This move is the most played. White needs to avoid the threat of capture on c4 followed by b7-b5.
1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. g1f3  3... d7d5  4. b1c3  4... a7a6 Carlsen has used this variation of the Queen's Gambit many times.