Nothing too tricky about this inference (author's opinion) question.
(B) sounds like the author's perspective. The author is all about broadening understandings. Remember how narrow the formalists were (lines 18-20)?
Wrong answers:
(A) has an extreme modifier. The author doesn't think any literary theory is limiting. In fact, the whole point of RRT is to be more open.
(C) has a problematic word. "Objective" sinks it. The whole point of RRT is subjective interpretations.
(D) has RRT all wrong. There's not one right "author-approved" meaning (see lines 26-32).
(E) is good until the comma. But the author is fine with readers using a theory to interpret text, so long as it's RRT.
I hope this helps. Post with questions.
Demetri