The ancient Nubians inhabited an area in which typhus occurred, yet surprisingly few of their skeletons show the usual evidence of this disease. The skeletons do show deposits of tetracycline, an antibiotic produced by a bacterium common in Nubian soil. This bacterium can flourish on the dried grain used for making two staples of the Nubian diet, beer and bread. Thus, tetracycline in their food probably explains the low incidence of typhus among ancient Nubians.

So I chose (D), because it most directly speaks to the evidence in the argument, "tetracycline in their food...'. However, I do not know whether this would be a valid GMAT question. (A) also provides a perfectly reasonable assumption on which the argument depends. If the tetracycline entered bodies after those bodies had been buried, then clearly it was not responsible for preventing typhus.

In GMAT-land, I can't remember seeing an assumption question in which two answer choices are assumptions upon which the argument depends, but one of them speaks more directly to the text/conclusion. If this is valid, and it is simply slipping my mind as to ever having seen such a question, surely this question is a 700+. I'd be interested to see if anyone has encountered a similar question. If so, then this is definitely a valid question, and a toughie .
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Will vote for D because

Question type : Assumption (Strengthen the conclusion)

conclusion : tetracycline in food explains the low incidence of typhus among ancient Nubians.

Premise 1: skeletons do show deposits of tetracyclinean antibiotic produced by a bacterium common in Nubian soil.

Premise 2: This bacterium can flourish on the dried grain used for making two staples of the Nubian diet, beer and bread.

A. The tetracycline deposits did not form after the bodies were buried.
--> one of the premise already state that "skeletons show the usual evidence of this disease", so option A cannot be true

B. The diseases other than typhus to which the ancient Nubians were exposed would not be affected by tetracycline.
--> Out of scope nothing talking about another diseases

C. Typhus is generally fatal.
--> Doesnot strengthe the conclusion.

D. Tetracycline is not rendered ineffective as an antibiotic by exposure to the process involved in making bread and beer.
--> Provide additional evidence that will strength the conclusion. If the Tetracycline which acts as antibiotic is not destroyed in the process of making bread or beer, then we can correctly conclude that
tetracycline in food probably explains the low incidence of typhus.
Correct

using ANT
Tetracycline is rendered ineffective as an antibiotic by exposure to the process involved in making bread and beer.
This clearly contradicts the conclusion, if Tetracycline doesnot act as antibiotic, then incidence of typhus would have been higher

E. Bread and beer were the only foods eaten by the ancient Nubians which could have contained tetracycline.
--> wrong because thay cannot be only source as they were made from grains and bacterium flourished on the dried grain.

Please substantiate your answer with reasoning. It will help.

Choice D is really the assumption of the argument. It defend the case that the tetracycline is exposed into ineffective form after processing through baker.
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such a tricky question
Now, I think D is the correct one. Both A and D look correct, but what makes D the correct one, is the part that says "Thus, tetracycline in their food probably explains..."

Use negate technique for choice A: The tetracycline deposits FORMED after the bodies were buried.

If the tetracycline formed after the bodies were buried, this kind of antibiotic still did not relate to the tetracycline that produced by bacteria in beer and bread.
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ChrisLele
The conclusion of this argument is "Tetracycline in their food probably explains the low incidence of typhus among ancient Nubians" as in the last sentence. This means that author expects food to be a reason for presence of Tetracycline. I understand that presence of tetracycline can be linked a defender kind of assumption, but we also know that tetracycline has always been there in Nubian soil, making me to go away from A, and the conclusion here should defend the low incidence of typhus( and not the presence of tetracycline on skeletons).
Let me know if this sounds logical or even if there is some flaw here.

The source of this question is a CR document from a gmatclub member. It says the question is from gmatclub or MGMAT. Just hoping for this to be true now
gmat-prep-critical-reasoning-collection-106783.html#p840353

IMO D

Because on negating A we get. The tetracycline deposits did form after the bodies were buried (Nothing told about scenario before bodies were buried). this implies two statements.
1) Tetracycline formed only after bodies were buried
2) Tetracycline formed both before and after bodies were buried

1 inverses the conclusion but 2nd does not inverse the conclusion.

Hence D

This is a valid GMAT question. However, if the gmat gives such a question, it will not include both choices A and D in the same question, because both are correct.

The same question has been asked, but in place of choice (A), a different choice has been stated. See here:
the-ancient-nubians-inhabited-an-area-in-which-typhus-occurs-44937.html

Again, in this question, both choice A and D are correct.

It was a tricky question!, but a good one. I choose A at the beginning but I was wrong. Reading carefully the conclusion and the premises that support D makes more sense.
First of all this is a causal argument:
Conc: Tetra in food --> probably explains low incidence of Typhus
P1: Skeletons of N show deposits of Tetra (antibiotic produced by a bacteria in N's soil)
P2: Bacteria can flourish on the dried grain used for making N diet: beer and bread.
P3: N inhabited an area with typhus, yet surprisingly few of their skeletons show evidence of this disease

Pre-thinking:
For a causal argument to be true:
-No other causes provoke the effect
-The effect doesn't cause the "cause"
-The cause happened before the effect.

Option A) The tetracycline deposits did not form after the bodies were buried. Incorrect
This option is apparently aligned with the latter one (sequence of events); however, option A doesn't talk about the real cause mentioned in the conclusion and supported by premises: Tetra in food. We know (from premises) that Tetra was indeed present in N's diet. So this is a real fact. Option a provides irrelevant information because even if Tetra deposits formed after the bodies were buried, the few evidence of the disease in the skeletons could or could have not happened because of Tetra in food.

Option D) Tetracycline is not rendered ineffective as an antibiotic by exposure to the process involved in making bread and beer. Correct
If the Tetra in food had loose its properties as an antibiotic after it was processed to beer and bread, It would have been ineffective to prevent the disease. So the few evidence of the disease in the skeletons would have been attributed to other causes.

Facts: few of the skeletons of Nubians show the usual evidence of the disease typhus even though they inhabited an area in which typhus occurred,. But their skeletons show deposits of tetracycline, an antibiotic produced by a bacterium common in Nubian soil. This bacterium can flourish on the dried grain used for making two staples of the Nubian diet, beer and bread.

Missing Information:There is no alternate explanation to what is shown in bold or it is not falsified, such as Tetracycline being rendered ineffective as an antibiotic by exposure to the process involved in making bread and beer.

Conclusion:Thus, tetracycline in their food probably explains the low incidence of typhus among ancient Nubians.

Choice D is the best match for the missing information.

Choice A seems very close. To eliminate one of the two, we have to focus on the reason for the conclusion. It is shown in bold. It means that the author believes that tetracycline was their in their food and this would eliminate A because choice A is more a premise. So actually attacking author's argument is showing tetracycline in the food is not responsible for the low incidence of the disease.
So the assumption of D saying that the tetracycline in the food is effective, is required.
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Option A can be clearly eliminated because " The skeletons do show deposits of tetracycline, an antibiotic produced by a bacterium common in Nubian soil". This statement means that irrespective of the skeletons that show deposits of tetracycline, the bacterium found in the soil produces tetracycline. So, tetracycline is always found in the soil irrespective of the presence of the deposits that were formed after the body was buried or before the body was buried.

There is one more point, which makes A weak as an assumption. If tetracycline deposited from the soil into the skeletons of these bodies, it still does not explain why only "few of their skeletons showed the usual evidence of typhus. After all, the ancient nubians inhabited in the area where typhus occurred, making them more susceptible to the disease. Most of them would have incurred the disease when they were alive. Typhus would invade their bodies when they were alive.

We can rewrite basic logical steps as follow:(each step is an effect of preceeding step)

1)Nubians lived where typhus occurred
2)Skeletons show few of them got affected
3)Skeletons have deposits of antibiotic
4)Bacterium produce antibiotic
5)Bacterium grows on grain
6)Grain is used to make staple food
7)Staple food has antibiotic
That's why typhus didn't affect many Nubians

We can see that only one answer choice, D, attacks this logical sequence.

To arrive from step 5 to step 7, we need an assumption mentioned in choice D

Posted from my mobile device
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The ancient Nubians inhabited an area in which typhus occurred, yet surprisingly few of their skeletons show the usual evidence of this disease. The skeletons do show deposits of tetracycline, an antibiotic produced by a bacterium common in Nubian soil. This bacterium can flourish on the dried grain used for making two staples of the Nubian diet, beer and bread. Thus, tetracycline in their food probably explains the low incidence of typhus among ancient Nubians.

Which of the following is an assumption on which the argument relies?

(A) The tetracycline deposits did not form after the bodies were buried.

(B) The diseases other than typhus to which the ancient Nubians were exposed would not be affected by tetracycline.

(C) Typhus is generally fatal.

(D) Tetracycline is not rendered ineffective as an antibiotic by exposure to the process involved in making bread and beer.

(E) Bread and beer were the only foods eaten by the ancient Nubians which could have contained tetracycline.

negating the main-point:
1. TT is not the reason for low traces of TY
given that a) TY is common disease b) TT found in staple food and is Anti-biotic to TY

pre-think:
1. what if Ty is not affected by TT because of something
2. what if Ty is not properly captured due to poor tech
3. what if some other pathogen has reduced the Ty after death

look at the options:
(A) The tetracycline deposits did not form after the bodies were buried.
even if TT came after burial, it could react to Ty and decrease it. hence loose end. incorrect

(B) The diseases other than typhus to which the ancient Nubians were exposed would not be affected by tetracycline.
discussion about other dieseases is irrelevant.hence incorrect

(C) Typhus is generally fatal.
it doesnot provide any clue !!.

(D) Tetracycline is not rendered ineffective as an antibiotic by exposure to the process involved in making bread and beer.
if TT is ineffective, it cannot kill Ty. hence it cannot be the reason of low traces of Ty. hence correct

(E) Bread and beer were the only foods eaten by the ancient Nubians which could have contained tetracycline.
even if bread and beer were not the only food source of TT, it doesnot imply anything at all!.

Hi,

I would like to add to the reasoning to opt out option A:
This option strengthens our conclusion. And negating this also weakens our belief in the argument. But the argument does not break down. Why? Because here we are just mentioning that deposits were made after burial. But did these depositions lead to low incidence of typhus? We don't know. We only know that there might be a possibility but this cause does not alter the other cause of the argument.

Basically, the causality is not shaken in presence of this cause.

One important point to note here is that, Option A talks about a cause which indeed weakens our conclusion when negated but does not break down the conclusion. Why?
Because we do not know that those traces caused low incidence of typhus.

A similar real-world analogy we could give is:

So many sixes by Virat in the last game probably explains India's comfortable Victory.

This argument is not broken down if we say, though it will weaken our belief in the above claim:
Dhoni hit 3 sixes in last over and we won the match.

This I say because what if due to Virat's sixes we were already comfortable and Dhoni just finished off the game in his style!!

So it's very much important to note that the cause will lead to the effect and it is very important to differentiate between weaken and break down.

Regards,
Rishav

I think it is very logical. The fact that deposits of tetracycline may have formed after a person was buried, does not mean that it is impossible for there to be a causal relationship between the food and the disease. Whereas if D were true, it would definitely not be possible.
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The ancient Nubians inhabited an area in which typhus occurred, yet surprisingly few of their skeletons show the usual evidence of this disease. The skeletons do show deposits of tetracycline, an antibiotic produced by a bacterium common in Nubian soil. This bacterium can flourish on the dried grain used for making two staples of the Nubian diet, beer and bread. Thus, tetracycline in their food probably explains the low incidence of typhus among ancient Nubians.

Which of the following is an assumption on which the argument relies?
Conclusion- tetracycline in their food probably explains the low incidence of typhus among ancient Nubians.

(A) The tetracycline deposits did not form after the bodies were buried.

(B) The diseases other than typhus to which the ancient Nubians were exposed would not be affected by tetracycline.- irrelevant, we are concerned whether tetracycline in food explains the low incidence of typhus

(C) Typhus is generally fatal.- irrelevant

(D) Tetracycline is not rendered ineffective as an antibiotic by exposure to the process involved in making bread and beer.

(E) Bread and beer were the only foods eaten by the ancient Nubians which could have contained tetracycline.- irrelevant, the argument claims tetracycline in food

I was down to options A and D and chose option A.

A on negation, The tetracycline deposits did form after the bodies were buried.
D on negation, Tetracycline is rendered ineffective as an antibiotic by exposure to the process involved in making bread and beer.
Both options seem like assumptions to me.

AjiteshArun , GMATNinja , MagooshExpert , GMATGuruNY , VeritasPrepBrian , MartyTargetTestPrep , DmitryFarber , VeritasKarishma , generis , nightblade354 other experts - please enlighten
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The ancient Nubians inhabited an area in which typhus occurred, yet surprisingly few of their skeletons show the usual evidence of this disease. The skeletons do show deposits of tetracycline, an antibiotic produced by a bacterium common in Nubian soil. This bacterium can flourish on the dried grain used for making two staples of the Nubian diet, beer and bread. Thus, tetracycline in their food probably explains the low incidence of typhus among ancient Nubians.

Which of the following is an assumption on which the argument relies?

(A) The tetracycline deposits did not form after the bodies were buried.

Skywalker18, Our conclusion is that tetracycline explains why there was a low incidence of typhus. Our premises give an indication as to why we discovered that tetracycline was in use by these people. (A) tries to attack a premise by saying that the buildup occurred after death, but does this destroy our argument? For one, another premise does say that tetracycline is in the soil, so that would actually strengthen our argument on that front. Second, not taking this into account, just because the buildup occurred after doesn't mean that the people didn't take it. It is equally as likely that they ate the grains even if the buildup wasn't on the bones. We would need another assumption about how tetracycline only builds up on bones if it is consumed. Our premise is being used to show a presence of an item, but just because the presence is questioned doesn't mean that it wasn't effective or in use.
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