Black has a number of options here. 5...e6 is probably safest, as 5...Nd7 allows the interesting pawn sacrifice, 6.e6 fxe6 7.f4. White will then look at moving the knights to d2, f3, g5 and e5, leaving black cramped and with a tough position.
For explanation of theory tables see theory table and for notation see algebraic notation.
1.e4 c6 2.d4 d5 3.e5 Bf5 4.Bd3 Bxd3 5.Qxd3
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