Exchange variations seem theoretically the best these days.
Queens-Gambit decline how should white counter

Exchange variations seem theoretically the best these days.
true but that allows black to play a famous trap

Exchange variations seem theoretically the best these days.
Really?
You could try the Catalan, theoretically strong and can be quite fun (albeit difficult) to play.

A) You exchange to play the exchange variation, not to win a pawn.
B) It's better to play the exchange with Nge2 (or some of the crazy g4 lines). Black is probably okay in the Nf3 variation, although he still must fear the minority attack.

See post #2, those lines are supposed to theoretically generate an easy edge for white. Yes, the catalan and orthodox variations are playable, but black seems to have some chances to equalize (lasker, tarkatower, etc.), or where in the catalan white only gains a small edge in some lines.
Of course black should employ this move order, when the exchange is not as strong, so catalan, orthodox, or Nf3 exchange must be played. However, black must be willing to play Nimzo-indian:

Your "study" of the QG must be going along slowly...
White's choices include the strong and flexible Nc3, Nf3, and g3 going for a Catalan position. Even if he wishes to play the Exchange Variation, he can play Nc3, since 3...dxc4 would make little sense for Black after 2...e6.
While Black will usually play ...dxc4 sooner or later if White does not preempt it, it is more advantageous for him to try to wait until White has moved the Bf1, since then the Bishop move will be turned into a lost tempo after Bxc4 recaptures.
when i posted this i knew there were moves i could do but i was wondering which was the best move as i first looked at the queens gambit accepted lines but now i am interested in the queens gambit declined lines

See post #2, those lines are supposed to theoretically generate an easy edge for white. Yes, the catalan and orthodox variations are playable, but black seems to have some chances to equalize (lasker, tarkatower, etc.), or where in the catalan white only gains a small edge in some lines.
Of course black should employ this move order, when the exchange is not as strong, so catalan, orthodox, or Nf3 exchange must be played. However, black must be willing to play Nimzo-indian:
err this topic is about what white should do after queens gambit declined not nimzo indian though
Hello right now im studying the queens gambit just wondering after black plays the declined variation how should white counter this