LSAT 13 – Section 4 – Question 05

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Type Tags Answer
Curve Question
PT13 S4 Q05
Must be true +MBT
+Hardest 145.536 +SubsectionMedium

This is a must be true question, since the stem asks: If the claims above are true, which one of the following must, on the basis of them, be true?

The first sentence begins by informing us that planetary bodies vary in what they’re composed of, but most of those in the Solar System have solid surfaces. It may be helpful to think of this sentence in terms of a superset, planetary bodies, and two overlapping subsets, planetary bodies in the solar system and planetary bodies with solid surfaces. The next sentence begins with the conditional indicator unless, and tells us that the renewal of the surface of a planetary body with a solid surface requires enough heat for volcanic activity. This is followed up with another conditional sentence, beginning with the indicator any, that tells that a solid surface planetary body that does not renew its surface will eventually become covered in craters like the moon. The stimulus ends by telling us some of the specifically old planetary bodies in the Solar System, such as Europa, have solid icy surfaces with very few meteorite craters. Interesting!

When we facing a MBT question with lots of conditionals and modifiers such as this one, its important to get a sense of the logic behind the text. We should look for how our conditionals can connect and relate to each other. In this case what we should notice is that if a planetary body doesn’t have a hot enough core, then it must be heavily marked by craters. Since we know some planetary bodies with solid surfaces are icy and not heavily marked by craters, then it must be true that some planetary bodies with icy surfaces have hot enough cores for volcanic activity. Let’s see if any of the answer choices resemble this pre-phrase:

Answer Choice (A) This is a good example of an answer choice where it is important to remember not to bring in outside knowledge to the LSAT. I’m sure many of you know that the moon isn’t icy, but it is still false that this must be true just based off our stimulus.

Answer Choice (B) Remember our different supersets and subsets. We’ve only been told that the renewal requirement applies to specifically solid surface planetary bodies, but this answer choice applies it to planetary bodies as a whole. It’s important to have picked up on the “such a planetary body” referential phrasing in the second sentence to avoid falling for this answer.

Answer Choice (C) We’ve been told nothing about the proportion of solid surface planetary bodies without lots of craters that are icy. For all we know they are all icy.

Answer Choice (D) We are only told about one of Jupiter’s moons, and that it is not heavily pockmarked.

Correct Answer Choice (E) This is exactly what we pre-phrased. If the only way for a solid surface planetary body to not be heavily marked by craters is to be hot enough for volcanic activity, and we’ve been told about a very cold solid surface planetary body that is not heavily marked by crates, then there must be at least some (i.e Europa) very cold planetary bodies with hot enough cores for volcanic activity.

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