As Black
Queen's Gambit Accepted
Black takes the c4 pawn, planning to give it back later, and in return develops freely and hits the centre with ...c5 or ...e5.
Lines
Against 3.e4: ...e5
1.d4 d5 2.c4 dxc4 3.e4 e5 4.Nf3 exd4 5.Bxc4 Bb4+ 6.Nbd2 Nc6
Classical line
1.d4 d5 2.c4 dxc4 3.Nf3 Nf6 4.e3 e6 5.Bxc4 c5 6.O-O a6 7.dxc5 Qxd1 8.Rxd1 Bxc5
Against 3.e3
1.d4 d5 2.c4 dxc4 3.e3 e5 4.Bxc4 exd4 5.exd4 Nf6 6.Nf3 Be7
With ...Bg4
1.d4 d5 2.c4 dxc4 3.Nf3 Nf6 4.e3 Bg4 5.Bxc4 e6 6.h3 Bh5
Against 3.e4: ...Nf6
1.d4 d5 2.c4 dxc4 3.e4 Nf6 4.e5 Nd5 5.Bxc4 Nb6 6.Bb3 Nc6