Student or Learner
If you watched the movie Avatar, you must be surprised at the scene when Neytiri and Jake were flying above the floating “Hallelujah Mountains.” And you thought Pandora’s world, Na’vi’s forested habitable moon, could not exist on the Earth. It cannot. However, the “Hallelujah Mountains” in Avatar were actually inspired by the Chinese mountains that exist in Yuanjiajie. If you have a chance to travel to China, you should witness the floating mountains in person.
Is this "should" presumption or obligation? I think the latter.