Main point question. Time to prephrase! We had the objectivists' opinion and the subjectivists' opinion and the fact that they can't seem to resolve their differences. Then we had the author saying the differences could be resolved if they just investigated the authority of their differing perspectives!
A: Talks about what the subjectivists should do. Subjectivists weren't the main focus of the passage. Eliminate.
B: Talks about what the objectivists have done. Objectivists weren't the main focus of the passage. Eliminate.
C: Wrong way to resolve the dispute.
D: Yes, identical to prephrase.
E: Eliminate for same reason as B. Objectivists weren't the main focus of the passage.