Queen's Gambit Accepted, how to continue after 3. e3 c6 I was playing Queen's Gambit Accepted. How should I continue after 3. e3 c6? I had no idea what to do after that.

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1.d4 d5 2.c4 dxc4 3.e3 c6
The simplest reply for white is Bxc4 which gives white exactly what he wants, a central pawn majority with tempo because he got his d4 pawn in the center plus his bishop on C4 while black basically doesn't have any pieces or pawns off their starting squares.

That said, a4 is probably also a good move as it makes b5 difficult for black.

Note that c6 isn't a great move for black because quite often in other lines he wants to move his c pawn straight to c5. If he ends up later playing c6-c5 then he has taken two moves instead of one to get there. Better for black would be e5, aggressively challenging white in the center or Nf6 fighting for the d5 and e4 squares.