Mature white pines

[ameyp12]

Mature white pines intercept almost all the sunlight that shines on them. They leave a deep litter that dries readily and they grow to prodigious height so that, even when there are large gaps in a stand of such trees, little light reaches the forest floor. For this reason white pines cannot regenerate in their own shade. Thus, when in a dense forest a stand of trees consists of nothing but mature white pines, it is a fair bet that:

Which one of the following most logically concludes the argument?

 

A) the ages of the trees in the stand do not differ from each other by much more than the length of time it takes a white pine to grow to maturity

 

B) the land on which the stand is now growing had been cleared of all trees at the time when the first of the white pines started growing

 

C) competition among the trees in the stand for sunlight will soon result in some trees' dying and the stand thus becoming thinner

 

D) other species of trees will soon begin to colonize the stand, eventually replacing all of the white pines

 

E) any differences in the heights of the trees in the stand are attributable solely to differences in the ages of the trees

 

 

 

 

OA:A

 

[GMAT2009]

I go with B.....because A, E talk of ages of trees...which is out of scope

D talks about other species ..but we don't have any information on other kinds of species . between B and C , C doesnot logically relate to stimulus

so i Go with B.

[ameyp12]

(A) The question presents a description of facts and then asks you to find a logical conclusion from those facts. The facts make clear that white pines cannot regenerate (re-grow) within their shade. This raises a question: how can they re-grow or grow in this environment? Choice A touches upon this problem: all of the trees must have started growing at roughly the same time because younger trees could not have grown below the canopy of older trees. (B) There is no evidence to prove this. ©, (D) and (E) are not relevant to the scope of the argument.

[cubicle]

It can only be A.

becuase conclusion should come from within the passage and not from outside information.

here the info within stimulus is 'mature' white pines intercept almost all of the sunlight and little light reaches forest floor. as a result pines can not regenerate in their own shades.

thus if we have a dense forest where there ain't any other trees but mature white pines then what can happen as logical conclusion? the prephrasing brings an answer like ' There will not be a generation after generation cultivation of 'mature' white pines' , the correct answer should reflect this prephrase somehow.

 

B----- out of scope as it brings outside info

C--- 'some trees dyin' can not be inferred

D----again can not be inferred

E---possible but here the stimulus talks about dense growing of 'mature' white pines and an effect of their blocking sunlight and not of their length.

 

So A clearly echoes the prephrase by showing that most of the trees in such a stand will be having equal ages as there will be no regeneration which is completely supported by the stimulus.

 

hence A wins.

 

HTH