Hi Shannon!
Must Be True-SN. The correct answer choice is (B).
Previous instructors already did a great job of explaining the diagram for this stimulus so I'll just sum up what they had here for reference when explaining the answer choices.
Sentence 1:
Literary classic 
Reveal something significant
Sentence 2:
Worthy of serious study Reveal something significant
Couple of notes here:
1) "Unworthy of serious study" can be on your diagram as stated or with a slash through "Worthy of serious study".
Unworthy of serious study =
Worthy of serious study
2) The wording of the 2nd sentence is tricky because of the use of the term "nothing." Think about a similar, simplified phrase: "Nothing that is A does B." If I were to diagram that statement, it would look like this:
A
B
Basically, it's stating that if you have characteristic A, you don't do B, because nothing with characteristic A does B.
It's the same thing here. Nothing that is unworthy of serious study reveals anything significant about the human condition is the same as saying that if you are unworthy of serious study, you don't reveal anything significant about the human condition. Because nothing in the group "unworthy of serious study" "reveals anything significant about the human condition."
Prephrase: we are trying to determine something that must be true based on the 2 conditional statements that we have. In a MBT question with conditional reasoning, we look for contrapositives and links between multiple conditional statements. We can link our 2 statements based on the common condition "Reveal something significant" if we take the contrapositive of our 2nd sentence:
Sentence 1:
Literary classic Reveal something significant
Contrapositive of sentence 2:
Reveal something significant Worthy of serious study
Chain and contrapositive chain:
Literary classic Reveal something significant Worthy of serious study
Worthy of serious study Reveal something significant Literary classic
Every relationship going forward along our chain and our contrapositive chain are relationships that MBT so we are looking for an answer choice that describes any one of those.
Answer choice (A): This answer choice says that if a book is worthy of serious study, then it is a literary classic. This goes backwards along our original chain and so it is a Mistaken Reversal (Worthy of serious study
Literary classic). (Diagramming Note: "Any" is a sufficient indicator.)
Answer choice (B): This is the correct answer choice. It accurately describes a relationship that must be true in our original chain, if we remove the middleman about revealing something significant (Literary classic
Worthy of serious study). (Diagramming Note: "only if" is a necessary indicator.)
Answer choice (C): This answer choice directly contradicts one of the must be true relationships in our original chain and so it is something that cannot be true (Literary classic
Worthy of serious study). (Diagramming Note: If "no literary classics are worthy of serious study", that is the same thing as saying that if you are a literary classic, you are not worthy of serious study.)
Answer choice (D): This answer choice goes backwards along our original chain. Therefore, it is something that could be true, but not something that we can prove must be true (Worthy of serious study
Reveal something significant).
Answer choice (E): This answer choice is similar to answer choice (D). It goes backwards along our original chain and is, therefore, something that could be true, but not something that must be true (Reveal something significant
Literary classic).
Hope this helps!
Best,
Kelsey
Reveals something significant