Hoping to rebound from an upsetting home loss to the Steelers, the Ravens flew to Texas Stadium for a Week 16 interconference duel with the Dallas Cowboys.  Baltimore would trail early in the first quarter as Cowboys running back Tashard Choice got a 2-yard touchdown run.  The Ravens would respond with a 26-yard field goal from kicker Matt Stover.  In the second quarter, Baltimore would take the lead as Stover made a 29-yard and a 37-yard field goal.  The Ravens would then use the third quarter to add onto their lead as rookie quarterback Joe Flacco completed a 13-yard touchdown pass to wide receiver Derrick Mason.  In the fourth quarter, Dallas would answer with kicker Nick Folk getting a 35-yard field goal, yet Baltimore equally answered with Stover's 35-yard field goal.  The Cowboys would try to rally as quarterback Tony Romo completed a 7-yard touchdown pass to wide receiver Terrell Owens, yet the Ravens immediately responded with running back Willis McGahee scoring on a 77-yard touchdown run.  Dallas tried to come back as Romo completed a 21-yard touchdown pass to tight end Jason Witten, yet Baltimore closed out the game with fullback Le'Ron McClain rushing for an 82-yard touchdown (the longest TD run by a Cowboys opponent in Texas Stadium). With the win, the Ravens kept their playoff hopes alive at 10-5.
Question: How many yards was the longest pass for a touchdown?
Answer: 21