PrepTest 117

Incorrect. There's no indication as to why this change happened—regulations loosening is just one explanation, so it can't be inferred.

Incorrect. Such a tempting answer choice! This would probably make it through our first past, and we'd need to circle back after reading the correct answer. So what's wrong here? It is true that it's easier for airborne illnesses to spread today than before 1985. However, that doesn't mean people are more likely to contract those diseases, as there are other factors involved. First, if there are fewer diseases around, or people are generally healthier, then there'd be fewer diseases to spread. There also might be better air filtration systems, or fewer people on planes. Or even a ban on smoking! Easier to spread isn't the same as more likely to contract, so this answer is incorrect.

Incorrect. This answer is too extreme in stating that it's "impossible" for illnesses to spread with low levels of CO2. While it may be harder for them to spread with lower levels of CO2 there's no indication that the "sliding scale" there goes all the way to 0% of spreading.

Incorrect. It's possible that the rate of replenishment has never been high enough to "protect" people from the effects of CO2 buildup. It does seem after all that there's almost always—if not always—a chance of an airborne illness spreading.

Correct. Argument or Facts:
Facts

Question Type:
Must Be True

Stimulus Summary:
Pre—1985 — Cabin air was replenished every 30 min
1985—Present — Cabin air replenished every hour
The less frequent the replenishment, the more CO2, the easier for illnesses to spread

Answer Anticipation:
This argument has two elements to it that we should look to to anticipate an answer—the timeline and the change that happened on it; and the relationship established in the last statement.

We know that cabin air is replenished less frequently now than it was before 1985. The last statement tells us a relationship based on less frequent replenishment—it means there's more CO2 in the air, and that means it's easier for illnesses to spread. So we can conclude that, compared to before 1985, there's more CO2 in planes now and thus it's easier for airborne illnesses to spread.

Let's find an answer bringing up one of those inferences!

Answer Explanation:
The less frequently air is replenished, the higher the level of CO2. On a flight of the same length, with the replenishment rate now 60 minutes vs. 30 minutes, the relationships established in that last line means that the planes now have more CO2 built up.

Key Takeaway:
Timelines are important on the LSAT. Things changing are important on the LSAT. Relationships are important on the LSAT. When you get statements that bring up these concepts, pay attention to them and see if you can make an inference by bringing them together.