Remember that scene in Star Wars: The Empire Strikes Back when the rebels are fleeing Hoth and Captain Lennox says, "Good, our first catch of the day."? Here is a clip to remind you, bit today, we are the EMPIRE!
So, White moved pawn to d4 (marked in yellow).
Early chatter on the #proj-chess_lab Slack channel (sign up here) is that the best move is cxd4*
I've included a few other ideas, but they are maybe all bad. Let's talk about what we think White will do, and how we might respond in the comments.
*I'm still learning chess notation! Apparently when you indicate the move of a pawn you don't need to specify a piece (like Pcxd4), because if no piece is indicated, that means it is a pawn. Also, the use of an "x" indicates a capture (OUR FIRST CATCH OF THE DAY!).