My take:
All those who keep a journal will be heard by the next generation. Some of these journal writers are true artists, others humorous observers of the commonplace, and still others insufferable egotists who feel compelled to record their every thought.
If the statements above are true, which one of the following must be true?
(A) Not all of those who are humorous observers of the commonplace will be heard by the next generation.Nowhere does it say that not all humorous observers keep a journal. So it's possible that all humorous observers keep a journal, meaning that it's possible that all humorous observers will be heard by the next generation. Could be true, but doesn't have to be.
(B) Everyone who will be heard by the next generation keeps a journal.Nowhere does it say that the next generation will ONLY hear those who keep a journal. It's possible that they also hear people who do not keep journals. Could be true, but doesn't have to be.
(C) The next generation will hear both insufferable egotists and true artists.Since some insufferable egotists and some true artists keep journals, and everyone who keeps a journal will be heard by the next generation, then it goes to say that the next generation will at least hear some insufferable egotists and some true artists (at least those who keep journals, since we know that at least some do). Has to be true.
(D) Some of those who keep journals are not true artists, humorous observers of the commonplace, or insufferable egotists.Nowhere does it say that the list given is exhaustive, and nowhere does it say that it isn't. It is conceivable that other types of people may keep journals as well, however it is also possible that these are the ONLY people that keep journals, and so that there are no other types of people who do. Could be true, but doesn't have to be.
(E) The next generation will bear some of those who are true artists but not all of them.Nowhere does it say that not all true artists keep journals. It's possible that they all do, so it's possible that the next generation will hear them all. Could be true, but doesn't have to be.
Let me know if I'm wrong.
Cheers,