Passages

I have been preparing for a few months now, and have realized that my critical reading score has slightly improved, but that the issue I face is that I get confused between two answer choices, and am unable to determine the correct one based on the passage. Aside from studying more vocab, how can I better completely understand the passage so that this doesn’t happen? I currently am in the 750 range for CR, but would really like to be at 780-800 before the October SAT which I think is possible.

Thank you