11. (c) No students were revising. Which students are being talked about in these sentences?
12.
13. The sentences refer to the students in a particular situation, a group who can be readily picked out by the intended hearer (or reader) of the sentence.
14. The second set doesn’t seem to have this effect. We don’t have to know anything about the whole set of tired entities, thirsty entities or revising entities in order to understand the sentence.