Chess Opening Theory/1. e4/1...c6/2. d4/2...d5/3. exd5/3...cxd5

= Caro-Kann Defence: Exchange Variation = This almost always leads to the Panov-Botvinnik Attack after c4, unless white plays 4.Bd3. Note that 4.Nc3?! would be a poor move due to the fact that the knight doesn't do much. e4 is poison, while e6 will turn d5 into a rock. Therefore, c4 followed by Nc3 in far better since then, there would be pressure on d5.

Theory table
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1.e4 c6 2.d4 d5 3.exd5 cxd5