Parallel questions have a highly regimented theory and approach – even if your core logical intuitions are very strong, following a routine process specifically built around the LSAT’s unique patterns will dramatically reduce the time and mental energy required to identify the correct answer. So review these lessons. They’re important.

In short, though, our approach will be to develop an abstract model of the stimulus’ argument, preserving the structure but not the subject matter, then take a shallow dip into the answer choices looking for structural mismatches. Usually that suffices to identify the correct answer, but sometimes we’ll need a deep dive to distinguish between the (usually just two) answer choices that remain after our shallow dip.

At its core, this is an eliminating options argument: there are exactly two options, and it’s not option 1, so it must be option 2.

P1: 9 - 5 calls are 15c (option 1)
P2: All other calls are 10c (option 2)
________
Con: If a call isn’t 10c (option 2), it’s 15c (option 1).

This argument structure is notable enough that it’s quite reasonable to roll into the answer choices with a low-resolution model, just looking for the one that follows the eliminating options pattern. I don’t even think you need to diagram anything at this point, since comparing the eliminating options structure to, say, a conditional chain, is straightforward to do in your head.

But it turns out the answer choices are all structured in a pretty eliminating-optionsy way. And in fact, they all start out with the exact same two-part opening sentence (for real: highlight the whole first sentence of (A) and hit ctrl+F), only differing in the conclusions they draw. Once you see that, you’ve gotta loop back around and build a more precise stimulus template, getting super clear on which puzzle pieces go where. Like this (plz don’t mock my handwriting I am very sensitive):

This is essentially the same structure as before – we’re just nailing down exactly which pieces the stimulus connects in its conclusion. Our conclusion doesn’t touch either sufficient (9 – 5) condition; it links the two necessary (15c and 10c) conditions together, saying “if not this, then that.”

As mentioned, all the answer choices share the same opening sentence, which sets up Premises 1 and 2. So let’s build a template for this Labs & Classrooms argument too:

In the above diagram, we get P1 and P2 from that shared first sentence, and then we proactively map out the appropriate conclusion to match our template from the stimulus, connecting the two necessary conditions with “if not this, then that.”

Now it’s time to go back to the answer choices and look at each last sentence. We’ve even got a sense of some probable wrong answers. For example, anything involving the sufficient conditions (Lab Work or /Lab Work) will be wrong.