If RC is an area of the GMAT with which you struggle, I would suggest going through the official guide and seeing what else can be gleaned from these questions, even if you have “done” them before.
This allows us to identify what the GMAC is teaching us to look for on the actual GMAT, and can really help you raise the bar on your abilities.
So, for example, let’s take the “terrestrial snakes” passage from the OG: https://gmatclub.com/forum/in-terrestrial-environments-gravity-places-special-demands-137034.html
And we’ll specifically look at this challenging Main Idea question:
In the passage,the author is primarily concerned with doing which of the following?
(A) Explaining adaptations that enable the terrestrial snake to cope with the effects of gravitational pressure on its circulatory system
(B) Comparing the circulatory system of the sea snake with that of the terrestrial snake
(C) Explaining why the circulatory system of the terrestrial snake is different from that of the sea snake
(D) Pointing out features of the terrestrial snake’s cardiovascular system that make it superior to that of the sea snake
(E) Explaining how the sea snake is able to neutralize the effects of gravitational pressure on its circulatory system
Our breakdown might look something like:
If you’re torn between 1 topic (terrestrial) versus 2 topics (terrestrial & sea snake), you can simply count the sentences and paragraphs in which each Topic appears (for example terrestrial appears in 3 paragraphs, while sea snake appears in 1). Also there are 3 sentences that say “terrestrial snake” (5 if we include “arboreal”!), and only 2 sentences that mention the phrase “sea snake”.
For informational passages, notice if one of the answer choice includes a keyword that is slightly more extreme than the other choices. The word “superior” should automatically knock out (D).
Don’t be afraid to look for a thesis. Sometimes the last sentence of the first paragraph will spell it all out: “That many terrestrial snakes in similar spatial orientations do not experience this kind of circulatory failure suggests that certain adaptations enable them to regulate blood pressure more effectively in those orientations.”