Why not 7.Qa4+ in Carlsen vs Navara QGD In the game of Carlsen vs Navara Biel Chess 2018, on move 7 why did Carlsen play e3 instead of playing Qa4+ and taking that hanging bishop?
I guess you mean the game below and at the 7th-move: 7.Qa4+ doesn't win the bishop because black can reply with Nc6 blocking the check and defending the bishop.

 [title "Biel, Carlsen vs Navara 2018"]
 [fen ""]
 [startply "12"]

 1.d4 Nf6 2.Nf3 d5 3.c4 e6 4.Bg5 Bb4+ 5.Nc3 h6 6.Bxf6 Qxf6 7.e3 (7.Qa4+ Nc6) O-O 8.Rc1 dxc4 9.Bxc4 c5 10.dxc5 Nd7 11.O-O Nxc5 12.Nb5 a6 13.Nbd4 b5 14.Be2 e5 15.Nc2 Rd8 16.Nxb4 Rxd1 17.Rfxd1 a5 18.Nd5 Qd6 19.Nxe5 Bb7 20.Bf3 Rc8 21.Ng4 Qf8 22.h4 Nd7 23.Rxc8 Bxc8 24.a3 h5 25.Nh2 g6 26.Be2 Ne5 27.Bxb5 Bb7 28.Nc3 Qe7 29.Rd4 Qe6 30.Nf1 Qb3 31.Rd2 Nc4 32.Rd7 Nxb2 33.Rxb7 Qxc3 34.Be8 Kf8 35.Bxf7 Qc6 36.Rxb2 Kxf7 37.Rd2 Qa4 38.Rd3 Qxh4 39.Rd7+ Kg8 40.Rd4 Qe7 41.a4 Qa3 42.g3 Qa1 43.Kg2 g5 44.Nd2 g4 45.Ne4 Qc1 46.Nf6+ Kf7 47.Nxh5 Qc6+ 48.Kg1 Qc1+ 49.Kh2 Kg6 50.Nf4+ Kf6 51.Ng2 Kg5 52.Rf4 Qd1 53.Nh4 Qc2 54.Nf5 Qd3 55.e4 Qd7 56.e5 Qh7+ 57.Kg1 Qg6 58.Nd6 Qe6 59.Rf5+ Qxf5 60.Nxf5 Kxf5 61.f4 gxf3 62.Kf2 Kxe5 63.Kxf3 Kf5 64.Ke3 1-0


In case white tries to further pressurise the knight on c6 after 7.Qa4+ Nc6, with e.g. 8.Ne5 black always has the option of taking on c3 first with check and then reacting to Ne5 with Bd7.