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2.g3. This fianchetto of the bishop signals White's attempt to control the central squares. It is the main line for tournament players. White continues with moves like Bg2, Nf3, 0-0, c4, Nc3.
2.Bg5. This makes 2...Nf6 doubtful, since 3.Bxf6 doubles Black's pawns and makes Black's game more difficult. Black usually plays 2...g6 to fianchetto his bishop before he plays Nf6. 2...g6 marks the Leningrad variation of the Dutch defence. White's bishop cannot trapped: 2...h6 3.Bh4 g5 4.Bg3 f4? 5.e3! Mate is threatened (6.Qh5#), so the pawn on f4 is won.
2.e4. This is Staunton's Gambit. After 2...fxe4 3.Nc3 Nf6 4.Bg5 d5 5.f3, White may or may not have enough for the pawn loss.