You are playing the Black pieces. Inventory your attacking options and what stops them from working. Your queen attacks White’s rook. Your bishop attacks White’s knight and pins it to White’s king. Your knight attacks White’s bishop. All of the attacked pieces have protection, but don’t stop there; look at the extent of the protection and its stability. The rook on b1 is guarded by White’s queen, so turn your attention to the guard: does the queen also have responsibility for something else that you might therefore be able to take? Yes; for one thing, it is the only guard of the bishop on f3 (the pinned knight is no defensive help). So Black plays NxB+. If White recaptures QxN (he shouldn’t—he should play Ke2), Black has QxR+.