When they had explored the lungs, Liz leaned up and tugged on Ms Frizzle's arm, gesturing for a moment. "Oh no! Looks like we're almost out of time. Alright, children. Although usually matter moves downwards through the esophagus and windpipe, there are two natural exceptions. Luckily for us, Valentine is displaying one of the less unpleasant of the two. Hold on -"

"ACHOO!"

Valentine sneezed out a full-sized schoolbus full of people.