In preparation for a large-scale tree-planting project, Thomasville

Question

In preparation for a large-scale tree-planting project, Thomasville has recorded the location, species, and condition of every tree in its downtown area. The results will be compared with results of the last such tree census, taken 20 years ago. Planting trees primarily from the species that turns out to have the best record of survival will assure downtown Thomasville of an abundant tree population 20 years from now.

Which of the following, if true, most seriously undermines the claim that the tree planting proposal will assure an abundant tree population?

A. because of the the strict laws governing industrial development, environmental conditions in Thomasville are unlikely to become harsher for trees than they have been during the last 20 years.

B. Thomasville has reliable records to show which trees in existence 20 years ago were cut down to permit new construction downtown.

C. A number of trees from one of the species widespread in Thomasville 20 years ago reached the end of their natural life span in the intervening period.

D. Very few species of trees grow as well in urban conditions as in natural conditions.

E. A city with a high proportion of an any one species of the trees can have its tree Population devastated by one outbreak of a disease.

ID 00834

GMATNinja · Accepted Answer

Samakshkapoor92 , when you answer a CR question (or an RC question, for that matter), your task is to find which answer choice is correct based on the  passage ,  not  on information that is contained in the other answer choices. Essentially, you should treat each answer choice as if it exists in a vacuum with only the text of the passage, and make your decisions one by one. So let's go through the options that are giving you trouble:

Remember, we are looking for a statement that "most seriously undermines the claim that the tree planting proposal will assure an abundant tree population." The proposal relies on data from 20 years ago and current data to determine which trees will most likely survive another 20 years. Answer choice (B) introduces a wrinkle in the data, which is that some of the trees that did not survive "were cut down to permit new construction." This, on the surface, sounds like it will create a problem for the proposal.

However, the answer choice doesn't merely state that some trees were cut down due to construction. It specifies that Thomasville  has reliable records  about exactly which trees were cut down. Can the fact that Thomasville has reliable records of this data undermine the proposal? Definitely not -- having reliable records could only help fix the complication that is introduced by the answer choice. You can eliminate (B) for this reason.

The goal of the "proposal" is to "assure downtown Thomasville of an abundant tree population 20 years from now." This answer choice tells us that a number of one particular species of tree died off naturally within the past twenty years. Is this because that kind of tree generally lives less than twenty years? Or because the trees were all planted at the same time more than twenty years ago? The first option would strengthen the proposal, while the second would call the data into question. We are not given enough information to determine the reason behind this statement, and therefore its effect on the strength of the proposal.

What we  do  know is that other types of trees  have  survived for the past twenty years, and that the proposal advocates planting those trees. So, answer choice (C) does not significantly undermine the proposal and we can throw it out.

Finally, take a look at the correct answer:

The proposal advocates planting trees "primarily from  the species  that turns out to have the best record of survival." Because one species will be planted more than the others, this answer choice significantly undermines the proposal. If the tree population can be devastated by one outbreak of a disease, then it is likely that Thomasville will not have an abundance of trees in twenty years if the town adopts the proposal.

Answer (E) is correct.

I hope this helps!

Samakshkapoor92 · Answer

gmat1393 ,  GMATNinja ,  GMATNinjaTwo ,  broall ,  nightblade354

guys,
can one of you explain why b is not the best choice, cant wrap the fact around my head that since c clearly shows that the data collected would be wrong or incomplete.

Mo2men · Answer

Dear  GMATNinja

Can you elaborate more on the highlighted part? I do not understand how the first strengthen and the second weaken. 
Thanks

GMATNinja · Answer

We cannot tell whether choice (C) undermines the claim that the tree planting proposal will assure an abundant tree population.

We could come up with a variety of hypothetical situations consistent with choice (C), for example:

1) Maybe the trees mentioned in (C) -- those that "reached the end of their natural life span in the intervening period" -- were all relatively young when they died. And  perhaps  because a bunch of those wimpy trees died in the intervening period, that species did not have the best survival record. So it is  possible  that, given (C), Thomasville ruled out a wimpier species in favor of a more durable one. Great!

2) But maybe the trees mentioned in (C) were actually a bunch of very old, durable trees that all just happened to reach the end of their natural life spans during the intervening period. And perhaps because a bunch of those strong/durable trees died in the intervening period, Thomasville decided not to plant that species. So it is  possible  that, given (C), Thomasville ruled out what may have been the most durable tree available. Bummer!

Then again, choice (C) only refers to "a  number  of trees." Is that a  significant  number? We have no idea. Maybe (C) only affects a few outliers and wouldn't affect the data analysis or the claim one way or the other.

The bottom line is that we have no reason to believe that (C) undermines the claim. As explained in  my last post , (E) clearly undermines the claim. So, (E) is a much better choice than (C).

tkorzhan1995 · Answer

GMATNinja , can you please help to explain how you were able to come up with two possible causes for C:
a) Survival rate is low--> Therefore, tress planted 20 years ago became extinct now--> Strenghthen argument that planting trees with high survival rate will result in abundance of trees 20 years from now; (I understand this cause. I was not able to come up with the second cause before reading your post);
B) Trees were planted more than 20 years ago. Could you please explain how you were able to come up with this cause?

GMATNinja · Answer

We're looking for an option that undermines the claim in the passage. When assessing a given answer choice, just ask yourself how the new information impacts that claim.

The information in (C) could impact the argument in several different ways -- as you've pointed out, if the trees just don't live long, then (C) would strengthen the argument. However, that reasoning assumes that the trees weren't  already  very old when the previous census was completed.

If you don't make that assumption, then (C) wouldn't strengthen the argument in the same way.

Additionally, as we pointed out in  this post , (C) talks about a "number" of trees. What does that mean? The cases you mentioned again make an assumption -- this time, that the "number" of trees is significant. In reality, (C) could be talking about a relatively  small  number -- in which case, (C) really wouldn't strengthen or weaken the claim.

To accurately think through how an answer choice impacts an argument, just be aware of any assumptions you're making. You want to assess the information on the page without relying on additional assumptions.

Because (C) could impact the argument in different ways, we can't say that it undermines the argument.

I hope that helps!

Engineer1 · Answer

Hi  KarishmaB   GMATGuruNY    MartyMurray , could you please provide feedback on my reasoning? Thank you!

In preparation for a large-scale tree-planting project, Thomasville has recorded the location, species, and condition of every tree in its downtown area. The results will be compared with results of the last such tree census, taken 20 years ago. Planting trees primarily from the species that turns out to have the best record of survival will assure downtown Thomasville of an abundant tree population 20 years from now.

Which of the following, if true, most seriously undermines the claim that the tree planting proposal will assure an abundant tree population?

A. because of the the strict laws governing industrial development, environmental conditions in Thomasville are unlikely to become harsher for trees than they have been during the last 20 years.   Strengthens, so eliminate.

B. Thomasville has reliable records to show which trees in existence 20 years ago were cut down to permit new construction downtown.   Irrelevant

C. A number of trees from one of the species widespread in Thomasville 20 years ago reached the end of their natural life span in the intervening period.
  This looks like a good answer choice to me. The only reason it is wrong is because of the fact that one of the species reached the end of lifecycle before 20 years (intervening perdiod). Moreover, if that species did not survive for 20 years, they probably   won't be even be available to be planted   (due to end of their life span). To me,   the purple colored fact makes   this answer choice irrelevant.

D. Very few species of trees grow as well in urban conditions as in natural conditions.   Irrelevant

E. A city with a high proportion of an any one species of the trees can have its tree Population devastated by one outbreak of a disease.   This is a reason that will be a blow to the projection / plan. Hence, correct.

MartyMurray · Answer

Makes sense.
 
This could be a strengthener since it serves to eliminate the possibility that they will misjudge which trees have the best record of survival by failing to account for the fact that some were cut down to permit new construction.
 
This choice has no clear effect on the argument. It basically means that some trees from one species died. OK, great. But how many is some? Three? Ten? We'd expect some trees from a species to die over a 20-year period even if most survived. So, this choice doesn't really tell us anything that makes a difference.

On another note, what you said about the trees of the species mentioned by this choice not being available to be planted doesn't apply. The passage does not say that the plan is to replant trees currently existing in the city. Given what the passage says, we can presume that the plan is to plant NEW trees primarily from the species that turns out to have the best record of survival.
 
Yes, an irrelevant comparison.
 
Yes, exactly.

Overall, your reasoning makes sense. You just need to be a bit more careful not to create an unsupported story as you did with (C).

agrasan · Answer

Hi experts  KarishmaB   GMATNinja   IanStewart   MartyMurray

I re-attempted the question and have a following reasoning to eliminate C.

If we look at the argument, it says "Planting trees...to have the best record of survival...downtown Thomasville of an abundant tree population 20 years from now."

Option C = "A number of trees from one of the species widespread in Thomasville 20 years ago reached the end of their natural life span in the intervening period."

Best record of "survival" itself means plants that were planted 20 yrs ago and are surviving till now so what option C says doesn't matter to us because it is already known/expected from the argument that some plants won't survive and may die in the intervening period, thus, option C doesn't provide us with valuable info to affect our confidence in the conclusion.

Please let me know if you agree with my reasoning or there is a mistake.

Axwe7 · Answer

MartyMurray

Hey Marty, I was tossed between B) and E). I see you've said earlier that B) could serve as a strengthener, while I understand your point, would you be able to opine on where my reasoning is flawed?

My reasoning on why I chose B) was that, by eliminating records that clearly and reliably show which trees were intentionally removed to make way for construction, the analysis of the data to find out which tree has the highest survival chance is tainted. This is because the lifespan of some trees has been truncated given the construction, and the actual survival likelihood remains unknown. Hence, the new trees that are planted could be based off flawed data ("undermines the conclusion"), which only displays the results of trees which haven't been removed due to construction.

Thanks and much appreciated!

MartyMurray · Answer

Hi  Axwe7 ,

I'm happy to help, but I don't fully understand your question.

Here's (B).

B. Thomasville has reliable records to show which trees in existence 20 years ago were cut down to permit new construction downtown.

To me that means that the town DOES have reliable records, meaning that the data is NOT tainted.

Does you agree with that interpretation?

MartyMurray · Answer

That reasoning captures exactly why (C) can be eliminated.

MartyMurray · Answer

In preparation for a large-scale tree-planting project, Thomasville has recorded the location, species, and condition of every tree in its downtown area. The results will be compared with results of the last such tree census, taken 20 years ago. Planting trees primarily from the species that turns out to have the best record of survival will assure downtown Thomasville of an abundant tree population 20 years from now.

This is a Plan question. So, our focus in analyzing the passage should be on the plan and the goal of the plan.

The plan involves the following:

recorded the location, species, and condition of every tree in its downtown area

The results will be compared with results of the last such tree census, taken 20 years ago.

Planting trees primarily from the species that turns out to have the best record of survival

The goal is the following:

assure downtown Thomasville of an abundant tree population 20 years from now

We see that the reasoning underlying the plan is that planting trees primarily from the species with the best record of survival will result in survival of the planted trees.

Which of the following, if true, most seriously undermines the claim that the tree planting proposal will assure an abundant tree population?

The correct answer will somehow indicate that, even though the trees planted will be primarily from the species with the best record of survival, the plan may not achieve the goal.

A. because of the the strict laws governing industrial development, environmental conditions in Thomasville are unlikely to become harsher for trees than they have been during the last 20 years.

This choice strengthens, rather than weakens, the case for success of the plan.

After all, if environmental conditions do not become harsher, than it makes sense that trees from a species with a good record of survival in the past will tend to survive in the future as well.

Eliminate.

B. Thomasville has reliable records to show which trees in existence 20 years ago were cut down to permit new construction downtown.

If anything, this choice strengthens, rather than weakens, the case for success of the plan.

After all, if Thomasville has reliable records to show which trees in existence 20 years ago were cut down to permit new construction downtown, then the records used in deciding which trees to plant will accurately indicate survival rates rather than be misleading because some trees didn't survive only because they were cut down.

Eliminate.

C. A number of trees from one of the species widespread in Thomasville 20 years ago reached the end of their natural life span in the intervening period.

This choice has no effect on the case for the plan.

After all, the point of the plan is to choose trees of a type that survived well.

All this choice indicates is that some trees, which were "widespread" and may or may not have been of the type that gets chosen for planting, didn't live forever.

Of course that fact doesn't affect the case for success of the plan since the plan is not based on the idea that all trees survive forever.

In evaluating this choice, it's helpful to notice that it doesn't even say how old the trees that "reached the end of their natural lifespan" were. For all we know, they were much older than 20 years.

So, this choice doesn't really add any useful information since it's common knowledge that trees don't live forever.

Eliminate.

D. Very few species of trees grow as well in urban conditions as in natural conditions.

This choice has no effect on the case for the plan.

After all, the point of the plan is to choose trees of a type with a good record of survival in Thomasville. So, regardless of whether many or few species of trees grow as well in urban conditions as in natural conditions, as long as the trees planted are ones that can be expected to survive in Thomasville, the plan could work.

Eliminate.

E. A city with a high proportion of an any one species of the trees can have its tree population devastated by one outbreak of a disease.

This choice is interesting.

The plan is to plant "primarily" trees from a species with a good record of survival in Thomasville under past conditions.

The issue is that, if what this choice says is true, that plan may not work.

After all, planting trees primarily from one species will result in a situation such that a high proportion of Thomasville's trees will be from one species. In that case, given what this choice says, Thomasville could have its tree population devastated by one outbreak of a disease.

In that case, the goal to "assure" downtown Thomasville of an abundant tree population 20 years from now will not be met by the plan because the trees planted will be vulnerable to devastation by disease.

Keep.

Correct answer   E

Axwe7 · Answer

Hmm i see. However, because there are reliable records to show that some trees have been removed. Doesn't this imply that the basis by which the person is trying to establish which trees have a better survival is flawed? It's an incomplete dataset.

MartyMurray · Answer

Every word matters in Critical Reasoning.

So, notice that your words don't quite match the words of the answer choice.

Here's what you said:

there are reliable records to show  that some trees  have been removed

Here's what choice (B) says:

Thomasville has reliable records to show  which trees  ... were cut down

What you said could indeed mean that the dataset is incomplete. However, what (B) says indicates that, while some trees were removed, the information regarding the trees in Thomasville is complete because information on "which" trees were removed is available.

In preparation for a large-scale tree-planting project, Thomasville

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In preparation for a large-scale tree-planting project, Thomasville

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