The phosphorus causes the stimulation of plankton growth near the ocean surface.
The plankton decay and fall to the floor, where bacteria eat them and consume oxygen.
This oxygen depletion means that few fish can survive in the region.
A
The agricultural runoff pouring out of the river contributes to the growth of plankton near the ocean surface.
B
Before phosphorus levels doubled in the ocean region, most fish were able to survive in that region.
C
If agricultural runoff ceased pouring out of the river, there would be no bacteria on the ocean floor devouring decaying plankton.
D
The quantity of agricultural runoff pouring out of the river has doubled in the past few decades.
E
The amount of oxygen in a body of water is in general inversely proportional to the level of phosphorus in that body of water.
Here we have an MSS question which we know from the question stem: The statements above, if true, most strongly support which one of the following, assuming that the widely accepted physical theories referred to above are correct?
We should note that the question stem tells us that we will encounter “widely accepted physical theories” in the stimulus, and that we will have to accept them as true in order to find our answer.
We start with a scientific phenomenon: there’s a black hole with a ring of gas orbiting around it. This ring of gas is emitting an x-ray that’s flickering as 450 times per second. You find yourself stopping right about now and wondering what the heck is going on here. Here’s the thing: I don’t know how gas rings emit x-rays, and fortunately, I don’t have to! It’s very easy to get lost in the science of a stimulus like this but if we just take this stimulus sentence by sentence, I promise you we’ll be able to ascertain everything we need to in order to succesfully answer the question.
The second sentence introduces us to the “widely accepted physical theory” referenced in the question stem. We’re told that the rate of flickering (of the x-rays) can best be explained if the ring of gas has a radius of 49 km. The LSAT is doing something tricky here: they are emphasizing the uncertainty of this theory by noting that it’s widely accepted (not universally) and using the phrase “best be explained” instead of something more definite. Here’s the thing: we don’t need to worry about the accuracy of this theory because the question stem tells us that we are “assuming [this theory] is true.”
So let’s look at these first two sentences together: black hole is orbited by ring of gas, x-rays flickering at 450 times per second, and a theory tells us that this means the ring of gas has a radius of 49 km. We already know that for our purposes, this theory is true. Therefore, we can say confidently: the ring of gas has a radius of 49 km.
Ok onto the third sentence. We’re told that the ring of gas could not maintain an orbit so close (i.e. 49 km away) unless the black hole was spinning. Well what does that tell us? The black hole must be spinning! The final sentence is phrased in such a way to suggest that this last piece of information is paradoxical or hard to reconcile with the previous two sentences–but it’s not! Our first two sentences have demonstrated that our ring of gas is 49 km away, and our third sentence tells us that given this proximity, our blackhole is spinning.
This stimulus is confusing because it is very hard to visualize. I’d definitely recommend drawing a diagram if that helps you. But at the end of the day, we have three straightforward, interconnecting facts: a ring of gas is emitting x-rays at a certain rate, that ring of gas must be 49 km away from the black hole (the black hole is at the center of the circle created by our gas ring, and radius is the distance from the center to the edge of a circle), but the gas ring couldn’t be 49 km away unless the black hole is spinning. Our simple, straightforward synthesis of this information is that the black hole, therefore, is spinning!
Answer Choice (A) We don’t know anything about rings of gas with a radius above 49 km. Our final sentence says that our gas ring couldn’t maintain an orbit so close without the black hole spinning. This doesn’t tell us anything about how the black hole would behave if the radius was larger.
Answer Choice (B) We simply know that there is one ring of gas in a stable orbit around a black hole that emits flickering x-rays. We do not have any conditionals here that tell us that this is the only type of ring of gas that emits flickering x-rays.
Correct Answer Choice (C) Great! This matches up with how we synthesized the stimulus. We have clearly outlined how our stimulus supports this answer choice.
Answer Choice (D) We don’t know what causes the black holes to spin. We know that the spinning of the black hole is connected to our gas ring maintaining a close orbit, but we have no information about a causal link between the x-rays and the spinning of the black hole
Answer Choice (E) We know that if a gas ring is orbiting around a black hole at a radius of 49 km, then the black hole is spinning. We don’t know anything about the way that black holes behave when they are orbited by a ring with a larger radius.
A ring of gas emitting X-rays flickering 450 times per second has been observed in a stable orbit around a black hole. In light of certain widely accepted physical theories, that rate of flickering can best be explained if the ring of gas has a radius of 49 kilometers. But the gas ring could not maintain an orbit so close to a black hole unless the black hole was spinning.
Summary
Scientists have seen a ring of gas that maintains a stable orbit around a black hole. The gas ring emits X-rays that flicker 450 times per second. This flickering speed suggests that the gas ring has a radius of 49 kilometers, meaning that it is very close to the black hole. However, for the gas ring to maintain its orbit so close to the black hole, the black hole itself must be spinning.
Strongly Supported Conclusions
In some conditions, gas can orbit black holes at a close distance.
The black hole is spinning.
A
Black holes that have orbiting rings of gas with radii greater than 49 kilometers are usually stationary.
This is unsupported. We know only that black holes that have orbiting rings of gas with radii of 49 kilometers must be spinning. We do not know the conditions of black holes that have orbiting rings of gas with radii greater than 49 kilometers.
B
Only rings of gas that are in stable orbits around black holes emit flickering X-rays.
This is unsupported. The stimulus only tells us about this particular ring of gas. We do not have any information about the emissions of any other rings of gas.
C
The black hole that is within the ring of gas observed by the astronomers is spinning.
This is strongly supported. We know that the gas ring has been observed in a stable orbit very close to the black hole. Because the ring can only maintain such a close orbit if the black hole is spinning, we can conclude that the black hole is spinning.
D
X-rays emitted by rings of gas orbiting black holes cause those black holes to spin.
This is unsupported. The stimulus tells us that the black hole must be spinning based on the observed facts of the gas ring. However, it does not tell us what causes the black hole to spin.
E
A black hole is stationary only if it is orbited by a ring of gas with a radius of more than 49 kilometers.
This is unsupported. We know only that a black hole orbited by a gas ring with a radius of 49 kilometers must not be stationary. We do not know the conditions required for a black hole to be stationary.
A
If there is neither government censorship nor boycotting of advertisers, there will be no restriction of the television shows that the public can watch.
B
Public boycotts could force some shows off the air even though the shows neither promote violence nor erode values.
C
For any television show that promotes violence and erodes values, there will be an audience.
D
There is widespread public agreement about which television shows promote violence and erode values.
E
Any action that leads to a restriction of what the public can view is censorship.
We’ve got a Main Conclusion question which we know from the question stem: Which one of the following most accurately expresses the main conclusion of the argument?
Moving onto the stimulus:
We start out with the notion that chemical fertilizers are very bad for a couple reasons: 1) they create health issues and 2) they kill worms, which are beneficial for soil.
Then we get the word “for” which some of you may recognize as an indicator that precedes a premise but is often part of a sentence that also includes a conclusion. Interesting. Is that the case here? Let’s take a closer look.
We’re told “for this reason.” What reason? Well “this reason” is a referential phrase referring to the second effect of chemical fertilizers we were presented with in the opening sentence. If we insert the information that “this reason” is referring to and paraphrase a bit, the second sentence would read like: “Because fertilizers destroy earthworms, the use of chemical fertilizers should be avoided.” So now we can see that the opening clause of this sentence provides support for the second clause. We can apply the why test just to make sure: Why should we avoid chemical fertilizers? Well because fertilizers destroy earthworms. The only way we can work out the full meaning of this sentence though, is by unpacking the referential phrase within it. Ok so we’ve identified at least one premise and conclusion. Now let’s move on to the third sentence.
If we look closely at the third sentence we see the word “thus” which is a conclusion indicator. But I thought we already found our conclusion? Not so fast! We found one conclusion! That doesn’t mean there can’t be more! When we take a closer look, we find a conclusion in the second clause of this sentence immediately following the word thus: “a garden rich in earthworms is much more fertile than a garden without them.” Working backwards we can see support in the first clause of this sentence. Again, we can apply the why test to test this support relationship: Why is a garden rich in earthworms much more fertile than a garden without them? Well because the castings they leave behind are richer than the soil they ingest. That works! First clause premise, second clause conclusion.
Ok so now we’ve got two conclusions, but only one of these can be our main conclusion meaning one of them is a sub-conclusion that both lends and receives support. If we take a step back, we see that the second conclusion supports the idea that chemical fertilizers should be avoided, meaning that this first conclusion about chemical fertilizers is our main conclusion. Let’s return once more to our old friend Mr. Why Test: Why should the use of chemical fertilizers be avoided? Well because our first premise tells us that fertilizers kill earthworms and our sub-conclusion tells us that a garden rich in earthworms is much more fertile than a garden without them. Now that’s what I call support!
Ok so let’s revisit our main conclusion: “the use of chemical fertilizers should be avoided.” Let’s take a look at our potential answers:
Answer Choice (A) This correctly sums up our premise but is not part of our conclusion.
Answer Choice (B) Again, this refers, correctly to another aspect of our premise, but is not found in our conclusion.
Answer Choice (C) Another answer choice that accurately sums up one of our premises, but not our main conclusion.
Correct Answer Choice (D) This is verbatim the main conclusion we identified. Not much more we need to discuss there. Case closed. But since we’ve still got one more answer choice left, let’s go ahead and take a look.
Answer Choice (E) Ok yet another answer choice that correctly sums up part of our stimulus. In this case this is referring to our sub-conclusion. If you didn’t recognize that this is a sub-conclusion that actually supports our main conclusion, this might be a tempting AC.