Question Type: Conditional
This question asks us what must be true given the condition that Sukanya receives exactly four emails. We’re always looking to follow the inference chain, but on "must be true" questions, we really want to follow it. At all costs, we want to avoid going through each answer choice, trying to show that it can be false; we simply don’t have time for that!
Let’s see what we can diagram here. Since there are only four slots, and we know either H or J must come first and last, this is a great candidate for framing. If we also consider that the HJ chunk must show up once, and that each element must be used, we can quickly come up with two completed frames:
Have we exhausted every possibility? Yes! Since positions one and four can only be H or J, we can be absolutely certain that we’ve left no stone unturned. Now we’re ready to look at the answer choices.
Answer (A) says that exactly one of the messages comes from L. Both of our diagrams have exactly on L, so we know that this does have to be true. We’ve found the answer!
Of course, on a real LSAT, we would move on immediately. But take just a moment to look at the other answer choices.
Notice a pattern? All of the wrong answers are things that are true in one of our frames, but not the other _ in other words, they could be true. If we hadn’t done such a thorough job filling in our diagrams, we’d be stuck wasting a lot of time trying to come up with scenarios in which these possibly true placements don’t occur.