At 2 points in Return Trip you were quizzed midway through the level, and therefore you had to answer various questions correctly and avoid getting 3 answers wrong at all costs.
Once you did get too many answers wrong, you would lose the quiz and would be forced to either survive a very difficult gauntlet, referred to both times as Deathcourses, or die trying and therefore have to restart the level.
While very difficult challenges you're much better off avoiding, both deathcourses have been beaten in their entirety without taking any hits, both times starting from the point where I got my 3rd answer wrong.
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