Fergusons Disease, a disorder in redwood trees that is marked by

Question

Ferguson’s Disease, a disorder in redwood trees that is marked by a nutrient deficiency, is caused primarily by infestations of the fungus E. Coli but can also be a result of the use of fertilizers, which contain synthetic insecticides. Therefore, fertilizers should only be used on redwood trees when the soil surrounding them is proved to be rich in nutrients.

Which of the following, if true, most strengthens the above argument?

A. E. Coli causes trunk and branch decay that can cause redwood trees to collapse when unsuspecting climbers attempt to climb infected trees.
B. Fertilizers themselves are often a significant source of nutrients.
C. There is no way for redwood trees to gain nutrients except through osmosis via the soil.
D. The effects of synthetic insecticides are sometimes indistinguishable from the effects of E. Coli.
E. Synthetic ingredients in fertilizers also impact the overall productivity and growth of trees.

Carcass · Answer

The author concludes that fertilizers should only be used on redwood trees when the soil surrounding them is proven to be rich in nutrients. This means that, in all other cases where the soil surrounding redwood trees is not proven to be rich in nutrients, fertilizers should not be used.

Which of the following, if true, most strengthens the above argument?

A. E. Coli causes trunk and branch decay that can cause redwood  trees to collapse when unsuspecting  climbers attempt to climb infected trees.
Irrelevant
B. Fertilizers themselves are often a significant source of nutrients.
I do not see any relation to our conclusion
C. There is no way for redwood trees to gain nutrients except through osmosis via the soil.
 Yes. In this case we can use the fertilizers 
D. The effects of synthetic insecticides are sometimes  indistinguishable from the effects of E. Coli. 
Irrelevant
E. Synthetic ingredients in fertilizers  also impact the overall productivity and growth of trees. 
Out

Regards

mysterymanrog · Answer

A) This maybe explains why the disease is dangerous, but does not help the authors argument. Out.

B) If anything, this weakens the argument. Since the disease is caused by a lack of nutrients, and if fertilzers are a source of nutrients themselves, why not use fertilizers everywhere? Out.

C) Correct. If the trees can only take in nutrients through the soil, then using fertilizers on trees that are planted in soil which has no nutrients will lead to trees that grow without nutrients, leading them to the infection.

D) This is extra information, but not relevant to the argument at hand.

E) Similar to D. Out.

Posted from my mobile device

durant25 · Answer

I do not get how C is correct. If anything, C tells us that fertilizers can be added because Osmosis is the only way (after adding fertilizer), and plants do osmosis meaning you can add it to the nutrient-deficient soil.
In D, if the effects are indistinguishable, then we do not add in nutrient-deficient soil because we cannot tell if it's E. coli or the fertilizer causing it.

guddo · Answer

Ferguson’s Disease, a disorder in redwood trees that is marked by a nutrient deficiency, is caused primarily by infestations of the fungus E. Coli but can also be a result of the use of fertilizers, which contain synthetic insecticides. Therefore, fertilizers should only be used on redwood trees when the soil surrounding them is proved to be rich in nutrients. 
 
Which of the following, if true, most strengthens the above argument?

The argument says fertilizers can help create the same disease they are meant to prevent or treat. So the conclusion limits fertilizer use to cases in which the soil is already rich in nutrients.  The key support  would show that redwoods depend on soil nutrients, so using fertilizer when the soil is not nutrient-rich is especially risky or ineffective.

(A) E. Coli causes trunk and branch decay that can cause redwood trees to collapse when unsuspecting climbers attempt to climb infected trees.

This is irrelevant. It describes a danger caused by E. Coli, but it does not explain when fertilizers should or should not be used.

(B) Fertilizers themselves are often a significant source of nutrients.

This weakens the argument. If fertilizers provide nutrients, then using them when the soil is not rich in nutrients may make sense.

(C) There is no way for redwood trees to gain nutrients except through osmosis via the soil.

This is correct. If redwoods can gain nutrients only through the soil, then the nutrient condition of the surrounding soil is crucial. This supports the idea that fertilizers should be used only when the soil is proved rich in nutrients, because  soil nutrient availability  is the key factor.

(D) The effects of synthetic insecticides are sometimes indistinguishable from the effects of E. Coli.

This does not strengthen the recommendation. It may make diagnosis harder, but it does not show that fertilizers should be used only when soil is nutrient-rich.

(E) Synthetic ingredients in fertilizers also impact the overall productivity and growth of trees.

This is too vague. “Impact” could mean help or harm, so it does not clearly support the argument.

Answer: (C)

egmat · Answer

Hi durant25,

I see exactly where the two answers got flipped for you. Let's slow down on what C is actually claiming.

Start with the argument's logic. Fertilizers  can cause a nutrient deficiency  (Ferguson's Disease). So the recommendation is a safety rule: only fertilize when the soil is  proven  rich in nutrients. To strengthen it, we need a reason why the soil's nutrient level is the thing that decides whether the tree survives.

Now read C literally:  "There is  no way  for redwood trees to gain nutrients  except  through osmosis via the soil." The key words are "no way... except." C isn't handing you a delivery mechanism that makes fertilizer safe - it's telling you the  soil is the tree's only source of nutrients . There is no backup.

That's what strengthens the rule. If a tree can  only  pull nutrients from the soil, then putting fertilizer on nutrient-poor soil is dangerous: the fertilizer may push toward deficiency, and the tree has no other way to make up for it. So proving the soil is nutrient-rich  first  becomes essential - exactly the author's recommendation. Your reading ("plants do osmosis, so you can add fertilizer anywhere") treats C as permission, but C is really a  constraint  on where nutrients come from.

On D:  "the effects... are sometimes indistinguishable" is only a  diagnosis  point - it tells you it's hard to tell which cause produced the disease  after the fact . But the recommendation isn't about diagnosing a sick tree; it's about  preventing  deficiency by controlling soil richness. D never links soil richness to prevention, so it does nothing to the argument's core - it's true-but-irrelevant.

A quick way to feel C: imagine a hiker who can get water  only  from one well. If a chemical you pour in might spoil that water, you'd insist the well be full and clean  before  adding it - because there's no other source. Turn one knob: if the hiker also had bottled water on hand, insisting on the well would matter far less. That "no other source" is precisely the force C adds.

Answer: C

Fergusons Disease, a disorder in redwood trees that is marked by

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Critical Reasoning (CR) Questions

Fergusons Disease, a disorder in redwood trees that is marked by

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards