Refusing a gambit is sometimes the wiser choice. But how ?
Black can refuse the Blackmar Diemer in various ways. I already covered 4..e3, 4...Bf5 and 4...e5. Let's look into 4...c5 (diagram) today.
White's next move is crtitical. 5.dxc5 exchanges queens but wins back the pawn - but this damages white's queenside considerably. Scheerer suggests 5.Bf4, but that is not really an option as balck gets the better play. That leaves 5.d5
Black strongest alternative now is 5...exf3 6.Nxf3 (diagram)
Black strongest move is now 6...g6.Scheerer now correctly indicates that white should not play 7.Bc4 and recommends 7.Bg5. However, my silicon assistant recommends 7.Bf4 (diagram)
After the obvious 7...Bg7, white has 8.Qd2 00 9.000 (diagram).
But now my system indicates 9...a6 gives black a small plus !? Seems there is some work to be done here !