Question a move in the "modern defence" against the king's gambit

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LargePawns

After exd5 the video im watching says Nf6 presumably to threaten the pawn, then Bc4 presumably to defend the pawn. What I don't understand is why can't the queen just take the pawn?? I'm relatively new to chess so this might be obvious to some but I can't see it. The queen taking the pawn also give black a lot of advantages (from my untrained eye).. 

KetoOn1963

 

LargePawns
KetoOn1963 wrote:

 

ahhh right right so white just gets more development if the queen takes, that makes sense

KetoOn1963
LargePawns wrote:
KetoOn1963 wrote:

 

ahhh right right so white just gets more development if the queen takes, that makes sense