Chess Opening Theory/1. e4/1...d5/2. exd5/2...Qxd5/3. Nc3/3...Qa5/4. b4/4...Qb6

While declining the gambit isn’t unsound, it is far less ambitious than accepting it. White continues to develop normally. Black shouldn’t take the b-pawn because that will give White a favourable version of the Leonhardt Gambit accepted, where she enjoys an extra tempo.