context: group of people sweeping the floor and cleaning
hypothesis: It is impossible that some janitors are sweeping floors and cleaning the campus late at night.
valid_hypothesis: It is impossible that some janitors are sweeping floors and cleaning the campus late at night.
invalid_hypothesis: It is probably the case that some janitors are sweeping floors and cleaning the campus late at night.
hypothesis_assertion: Some janitors are sweeping floors and cleaning the campus late at night.