Hm. I see your point!

Wait... no. No, I don't. Moving on...


The author describes the method in the first paragraph and then, in the second paragraph, explains a couple limitations of that method. The author does not imply that the method is invalid or that it should not be used. Rather, the author explains how climatic conditions can be deduced from tree-ring patterns and then describes conditions under which that method would not be reliable. In other word, the author believes that the method is valid but that it doesn't work under certain circumstances.

So the main purpose is to describe how (and under what conditions) the method can be used, not to question the validity of the method.

So choice (C) is more accurate than choice (B).

I hope this helps!
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In 2:55 minutes,
The rings are the main clues for understanding the age of a tree, the various shapes of the rings formed changes with the change of weather (water supplied to it, in different climatic condition).So, clearly it triggers the fact that the rings are the only link to find the age and if due to some reason the rings are uncertain to figure out by the researchers then it brings lack of correlation , i.e tree rings and its age.

In opening line it says "Dendrochronology, the study of tree-ring records to glean information about the past, is possible because each year a tree adds a new layer of wood between the existing wood and the bark."-------means every year tree adds a new layer (ring)

In last but one line it says "And trees in extremely dry regions may go a year or two without adding any rings, thereby introducing uncertainties into the count." ------means the regular pattern of "one ring per year" phenomenon may be not shown due to extremely dry weather.

So if scientists count the age of tree by counting number of rings and if the tree is having sometimes two rings in a year or no ring at all in any given year, this may lead to wrong age determination of the tree.


Hence E.

HTH

Why B is wrong ?
Clearly, the second paragraph is questioning the validity of method explained in first paragraph.

The passage is primarily concerned with
(A) evaluating the effect of climate on the growth of trees of different species
(B) questioning the validity of a method used to study tree-ring records
(C) explaining how climatic conditions can be deduced from tree-ring patterns
(D) outlining the relation between tree size and cell structure within the tree
(E) tracing the development of a scientific method of analyzing tree-ring patterns

The passage suggests which of the following about the ring patterns of two trees that grew in the same area and that were of different, but overlapping, ages?
A. The rings corresponding to the overlapping years would often exhibit similar patterns.
B. The rings corresponding to the years in which only one of the trees was alive would not reliably indicate the climate conditions of those years.
C. The rings corresponding to the overlapping years would exhibit similar patterns only if the trees were of the same species.
D. The rings corresponding to the overlapping years could not be complacent rings.
E. The rings corresponding to the overlapping years would provide a more reliable index of dry climate conditions than of wet conditions.

I didn't understand this answer.

Passage states something about dead tress of different, but overlapping, ages.

How can a question ask about trees in general that grew in the same area and that were of different, but overlapping, ages.

So how about answering this one then?

Took 6 mins 10 seconds , including 2 mins to read the passage

-The author talks about a certain study that can be used to determine climatic conditions
-The study also talks about how aging is related to the number of rings a tree has
-The author does not offer an opinion and is merely stating facts



1.
"And trees in extremely dry regions may go a year or two without adding any rings, thereby introducing uncertainties into the count."
The rings of trees are used to determine the age of the trees and since there are no rings appearing on trees in dry regions, we cannot be sure on the age of the tree and hence there will not be a perfect correlation between age of tree and number of rings. Hence option (E)

2.
―Often, ring patterns of dead trees of different, but overlapping, ages can be correlated to provide an extended index of past climate conditions"
For 2 trees to be correlated they should have common features arising from their ring patterns which eventually indicate the climatic condition they grew in. Option (A) clearly states this point and hence is the right answer.

3.
The author is clearly concerned with determining how rings on trees can be used to predict past climactic conditions

Answer C
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Can someone explain?
I don't see how C Is the main point.
First dendrochronology was introduced and then it was questioned in the second paragraph.
if you take C as the answer it is missing the most of the second paragraph.

P1 - about D, how rings form in diff condition.
P2 - what if no change in climate; uncertainties;
Main point - explained D, impact of weather on rings, and uncertainties.
Tone - informative.

1. In the highlighted text, "uncertainties" refers to
pre-think - due to dry condition, how rings are not added.

(A) dendrochronologists' failure to consider the prevalence of erratic weather patterns - no
(B) inconsistencies introduced because of changes in methodology - no; changes in methodology- wrong
(C) some tree species' tendency to deviate from the norm - true but not the answer.
(D) the lack of detectable variation in trees with complacent rings - no
(E) the lack of perfect correlation between the number of a tree's rings and its age - yes; because of uncertainties introduced.

-------------------------------------------
2. The passage suggests which of the following about the ring patterns of two trees that grew in the same area and that were of different, but overlapping, ages?

Often, ring patterns of dead trees of different, but overlapping, ages can be correlated to provide an extended index of past climate conditions

(A) The rings corresponding to the overlapping years would often exhibit similar patterns. - has to be this
-------------------------------------------
3. The passage is primarily concerned with

(A) evaluating the effect of climate on the growth of trees of different species - evaluating is +/- of something.
(B) questioning the validity of a method used to study tree-ring records - questioning is only a part.
(C) explaining how climatic conditions can be deduced from tree-ring patterns - not perfect but covering most of the passage. use of vocab is also moderate "explaining".best of the lot.
(D) outlining the relation between tree size and cell structure within the tree - sub part of P1
(E) tracing the development of a scientific method of analyzing tree-ring patterns - tracing the development of a scientific method --- well not working on a method.
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"The rings corresponding to the overlapping years could not be complacent rings." what's the meaning of this complacent rings??

GMATNinja

For Question2:

Basis this line in the passage "Certain species sometimes add more than one ring in a single year, when growth halts temporarily and then starts again."

Shouldn't the answer be :
(C) The rings corresponding to the overlapping years would exhibit similar patterns only if the trees were of the same species.

As (A) does not talk about any species?

To choose (C), we need to find support in the passage indicating that ring patterns between overlapping trees are ONLY similar if those trees are of the same species.

In other words, NO two trees of different species would exhibit similar patterns in the years in which they overlap.

As you point out, the passage mentions that "certain species" have different ring growth patterns. But does that mean that ring patterns are ONLY similar amongst trees of the same species?

Not necessarily. It is entirely possible that some, or even most, tree species exhibit similar patterns in the same year -- even if certain trees have different patterns. Because the passage doesn't indicate that ring patterns are similar ONLY if trees are of the same species, (C) is out.

I hope that helps!
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For Q1, can someone please explain why C is wrong?
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"Uncertainty" is about the age of trees. We already know that they have already deviated from the norm, from that we have an uncertainty of the age.
We can get it from the last line from the last paragraph "ages can be correlated to provide an extended index of past climate conditions." Ages can be correlated from the rings, but when there is an uncertainty about the age of the trees.

When I read the sentence complacent rings, I thought of meaning as similar. But on checkingdictionary.com I found the meaning as : self-satisfied, pleased .

I don't see similar or synonyms of similar in complacent meaning list.
Can someone give his/her opinion on meaning of D with the dictionary meaning?

Hi imSKR,

Dictionary meaning of Complacent: showing smug or uncritical satisfaction with oneself or one's achievements.
Other synonyms in addition to ones you have mentioned are lazy, slack.

Now w.r.t the passage, it would mean slow changes in the rings or no changes at all, as also mentioned in the last para:
However, trees that grew in areas with a steady supply of groundwater show little variation in ring width from year to year; these "complacent" rings tell nothing about changes in climate.

Hope This Helps.
Thanks.