How will the right answer fit in terms of support and conclusion?

Only the right answer will be support that must be true if the conclusion is true. More simply, only the right answer will be support that doesn’t bring in anything new.

Highlight the main conclusion in the passage, if there is one:

this practice clearly should be acceptable

[BACKGROUND]. But [CONCLUSION], because [SUPPORT].

Whoa, where’d the author get “acceptable” from? That just showed up in the conclusion, even though they didn’t mention or explain what’s acceptable anywhere else in the passage. In other words, the conclusion changed the subject. The right answer will connect “acceptable” to the support about “raising its prices to unreasonable levels”.

Map the wording of the answers to the wording of the passage:

(A) Any company that is successful will inevitably…

This is making a really extreme statement. It’s about every single “successful” company, everywhere, all the time, with no exceptions. And it doubles down on that by saying the result will happen no matter what, in every single case, with no exceptions. There’s no way that must be true based on this argument that’s only about “predatory pricing”.

(B) …will engage in predatory pricing simultaneously.

The passage doesn’t say anything about them going one at a time or doing it all at the same time. You’d have to add in your own reasoning to connect that to whether predatory pricing “should be acceptable”. No way the argument “depends” on that.

(C) …the largest and wealthiest companies…

…are never mentioned. Nothing about them would have to be true based on the conclusion, since there’s no clear connection between them and whether predatory pricing “should be acceptable”.

(D) It is only competition or the threat of competition…

There could totally be other things that keep companies from raising prices. Just because the passage only mentioned a couple doesn’t mean those are the “only” ones.

(E) Any pricing practice that does not result in unreasonable prices should be acceptable.

This is the only answer that even mentions what’s “acceptable”. That makes the choice pretty clear. But all of this maps really well. The only reason the author gave why predatory pricing is “acceptable” was preventing “unreasonable prices”, so they must think that reason is enough all by itself. And that’s exactly what this answer is saying.

(E) is the correct answer.