Critical Reasoning

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 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 any one species of trees can have its tree population devastated by one outbreak of a disease.

The solution below is taken from the GMATFix App.



-Patrick

GMATGuruNY wrote:

BlueDragon2010 wrote: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 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 any one species of trees can have its tree population devastated by one outbreak of a disease.

This answer choice makes an analogy between the PAST and the FUTURE.

Plan: To plant primarily Thomasville's star tree: the species of tree that has the best record of survival OVER THE PAST 20 YEARS.
Goal: To assure a high tree population 20 YEARS FROM NOW.
Assumption: Over the past 20 years = 20 years from now.

To weaken the analogy -- and thus the plan -- the correct answer choice will show how the NEXT 20 YEARS might differ from the PAST 20 YEARS.

Answer choice E: A city with a high proportion of any one species of trees can have its tree population devastated by one outbreak of a disease.
This answer choice explains how the next 20 years will differ:
Since the tree population will consist primarily of ONE species, it could be wiped out by ONE outbreak of disease -- WEAKENING the conclusion that Thomasville will have a high tree population 20 years from now.

The correct answer is E.

Dear Mitch,

1- Why choice C is wrong?

2- In the question itself, it is mentioned 'spices' , Is 'species' singular or plural or debatable issue? does it mean different kinds or only one type of species ? In light of your answer to my question, does the OA consist in number with mentioned in question 'primarily from the species that turns out to have'?

Thanks