Chess Opening Theory/1. e4/1...c6/2. d4/2...d5/3. exd5/3...cxd5/4. Bd3

= Caro-Kann Exchange Variation = Nc6 is most common here, threatening the pawn.

Theory table
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1.e4 c6 2.d4 d5 3.exd5 cxd5 4. Bd3