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# Dendrochronology, the study of tree-ring records to glean information

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Dendrochronology, the study of tree-ring records to glean information  [#permalink]

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Updated on: 02 Sep 2019, 03:26
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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. In temperate and subpolar climates, cells added at the growing season's start are large and thin-walled, but later the new cells that develop are smaller and thick-walled; the growing season is followed by a period of dormancy. When a tree trunk is viewed in cross section, a boundary line is normally visible between the small-celled wood added at the end of the growing season in the previous year and the large-celled spring wood of the following year's growing season. The annual growth pattern appears as a series of larger and larger rings. In wet years rings are broad; during drought years they are narrow, since the trees grow less. Often, ring patterns of dead trees of different, but overlapping, ages can be correlated to provide an extended index of past climate conditions.

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. And trees in extremely dry regions may go a year or two without adding any rings, thereby introducing uncertainties into the count. Certain species sometimes add more than one ring in a single year, when growth halts temporarily and then starts again.
1. 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.

2. In the highlighted text, "uncertainties" refers to
A. dendrochronologists' failure to consider the prevalence of erratic weather patterns
B. inconsistencies introduced because of changes in methodology
C. some tree species' tendency to deviate from the norm
D. the lack of detectable variation in trees with complacent rings
E. the lack of perfect correlation between the number of a tree's rings and its age

3. 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

Originally posted by PiyushK on 12 Aug 2014, 07:05.
Last edited by SajjadAhmad on 02 Sep 2019, 03:26, edited 2 times in total.
Updated - Complete topic (379).
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Re: Dendrochronology, the study of tree-ring records to glean information  [#permalink]

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24 Jan 2018, 19:22
4
1
Shivikaa wrote:
hi,
Also, I didn't understand Q1.

Quote:
1. 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.

For the first question, refer to the following portion: "In wet years rings are broad; during drought years they are narrow, since the trees grow less. Often, ring patterns of dead trees of different, but overlapping, ages can be correlated to provide an extended index of past climate conditions."

So if we look at the ring patterns of dead trees, we should be able to tell which years were dry and which years were wet based on the width of the rings. If we only have one tree, then we would obviously only be able to gather data for the years in which that tree was alive. But now imagine we have two trees. One of the trees died in 1940 at the age of 50, and the other was born in 1950 and lived for 60 years (a 10 year overlap). In that case, we would have ring data from 1890 - 2010 and could use that data to help figure out which years were wet and which were dry.

Now consider the 10-year overlap. Because we are talking about different trees, the actual widths of the rings from those years might not be exactly the same. However, during wet years, we would expect RELATIVELY broad rings. During dry years, we would expect relatively narrow rings. So even though the precise widths might not be exactly the same for both trees, the PATTERNS (i.e. narrow-narrow-broad-narrow-broad-broad-broad-etc) will likely be the same. Now the second paragraph does explain why this is not ALWAYS the case, but the passage suggests that the patterns will OFTEN exhibit similar patterns.

Hopefully that helps you arrive at the correct answer!

Quote:
2. In the highlighted text, "uncertainties" refers to
A. dendrochronologists' failure to consider the prevalence of erratic weather patterns
B. inconsistencies introduced because of changes in methodology
C. some tree species' tendency to deviate from the norm
D. the lack of detectable variation in trees with complacent rings
E. the lack of perfect correlation between the number of a tree's rings and its age

The highlighted portion specifically refers to trees that may go a year or two without adding rings. According to the first paragraph, it is often possible to determine a tree's age by counting the rings. Why? Because there is typically an annual boundary line at the end of the growing season. With a regular annual growth pattern, you can count the rings to determine the age.

But what if a tree goes a year or two without adding any rings? In that case, if you count the rings to determine the age, your number will be LESS than the tree's actual age. For example, if you count 40 rings, the tree could actually be 41, 42, 45, 50, or 60+ years old! We would have no way to determine the number of years in which rings were not added. This corresponds to choice (E).

As for choice (D), the highlighted portion refers to the uncertainty in ring count, not to the lack of variation in ring width in complacent trees. We are indeed told that trees with "complacent" rings show little variation in ring width from year to year. However, you should still be able to count rings to determine the AGE of complacent trees. You would not be able to tell which years were wet/dry, but you should still be able to determine the age.

Choice (E) is the best answer.
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Re: Dendrochronology, the study of tree-ring records to glean information  [#permalink]

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14 Aug 2014, 14:54
Time taken: 05:10mins

1. 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.Sort of. But the option is too wide in scope. This option adds climate conditions and a lot more in "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.No we need both the trees to be alive to analyse climate conditions
C. The rings corresponding to the overlapping years would exhibit similar patterns only if the trees were of the same species.Its not necessary to be the same species
D. The rings corresponding to the overlapping years could not be complacent rings.They can be
E. The rings corresponding to the overlapping years would provide a more reliable index of dry climate conditions than of wet conditions.Correct.

2. In the highlighted text, "uncertainties" refers to
A. dendrochronologists' failure to consider the prevalence of erratic weather patternsUncertainty is wrt the determination of age of tree in years of drought or sporadic growth spurts
B. inconsistencies introduced because of changes in methodologyThere is no mention of change in methodology
C. some tree species' tendency to deviate from the normSort of. But this makes it sound like the tree deviates intentionally. Sometimes, like in cases of drought, trees are compelled to introduce inconsistent ring patterns.
D. the lack of detectable variation in trees with complacent ringsNope
E. the lack of perfect correlation between the number of a tree's rings and its ageYes. Sometimes due to climate or owing to the species that the tree is, there is inconsistencies with the tree-ring patterns.

3. The passage is primarily concerned with
A. evaluating the effect of climate on the growth of trees of different speciesWe are not discussing different species here.
B. questioning the validity of a method used to study tree-ring recordsWe are not questioning anything. It is just a description of the method
C. explaining how climatic conditions can be deduced from tree-ring patternsCorrect.
D. outlining the relation between tree size and cell structure within the treeThere is no mention of tree-size contributing to ring formation. Only age is introduced as a factor.
E. tracing the development of a scientific method of analyzing tree-ring patternsWe do not have any explanation of history of method of analysing tree-ring patterns
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Re: Dendrochronology, the study of tree-ring records to glean information  [#permalink]

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14 Aug 2014, 23:33
1. 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.

Ans - D

In the passage it is stated that often, ring patterns of dead trees of different, but overlapping, ages can be correlated to provide an extended index of past climate conditions. Start of second passage states that "complacent" rings tell nothing about changes in climate. Hence it can be deduced that rings corresponding to overlapping years couldn't be complacent rings.

2. In the highlighted text, "uncertainties" refers to
A. dendrochronologists' failure to consider the prevalence of erratic weather patterns
B. inconsistencies introduced because of changes in methodology
C. some tree species' tendency to deviate from the norm
D. the lack of detectable variation in trees with complacent rings
E. the lack of perfect correlation between the number of a tree's rings and its age

Ans - D

First paragraph states how temperature and climate systematically affect tree growth. Start of second paragraph states that 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. So these trees don't exhibit the typical variations due to climate and temperature changes that trees would normally exhibit.

3. 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

Ans - C

Author outlines how the methods of Dendrochronology are used and in second paragraph he mentions certain limitations of their applicability.
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Re: Dendrochronology, the study of tree-ring records to glean information  [#permalink]

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28 Sep 2014, 06:23
2
desaichinmay22 wrote:
PiyushK wrote:
5min 10sec

A E C (all correct)

OA also updated.

Can you please explain question 1. A seems too strong to be the correct answer. We don't know whether trees would exhibit similar patterns. Since comparison of ring patterns different tress with overlapping ages can provide extended information, we can say that these rings are not complacent rings.

That is the reason why the author is saying that ring patterns are corroborated among trees and conclusion about climatic conditions can be arrived at. There will be differences between two trees, but majority will exhibit the similar pattern and that is what Option A) is saying.
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Re: Dendrochronology, the study of tree-ring records to glean information  [#permalink]

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20 Jan 2018, 22:17
hi,
Also, I didn't understand Q1.

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Re: Dendrochronology, the study of tree-ring records to glean information  [#permalink]

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27 Jan 2018, 11:03
Hi GMATNinja

I don't quite understand the example you mentioned in your post.

"One of the trees died in 1940 at the age of 50, and the other was born in 1950 and lived for 60 years (a 10 year overlap)"

If one tree died in 1940, and the other was born in 1950, then it would be a 10 year short instead of a 10 year overlap.

Am I correct?
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Dendrochronology, the study of tree-ring records to glean information  [#permalink]

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09 Dec 2019, 06:00

what's the problem of the B in Q3?

IMOP, P1 states general patterns of rings under different environments,
while, P2 says patterns are similar under certain environment, and under some other certain environments, pattern has "uncertain" pattern, question the accuracy of the age if count the rings.
because I think Q2 questions the patterns, so I picked up B,
I think C does not include what P2 says, so I cross off C
I saw B is the second ranking, suggesting not few people agree with B.
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Re: Dendrochronology, the study of tree-ring records to glean information  [#permalink]

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21 Dec 2019, 22:18
all correct and in 7m12s. thank you for posting.
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Dendrochronology, the study of tree-ring records to glean information  [#permalink]

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12 Jan 2020, 00:02
Hi GMATNinja

I don't quite understand the example you mentioned in your post.

"One of the trees died in 1940 at the age of 50, and the other was born in 1950 and lived for 60 years (a 10 year overlap)"

If one tree died in 1940, and the other was born in 1950, then it would be a 10 year short instead of a 10 year overlap.

Am I correct?

2 years late but I have the same question. If one tree dies in 1960 and the other was born in 1950 then only there will be a 10 year overlap. Isnt it?
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Dendrochronology, the study of tree-ring records to glean information  [#permalink]

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24 Jan 2020, 23:20
GMATNinja wrote:
Shivikaa wrote:
hi,
Also, I didn't understand Q1.

Quote:
1. 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.

For the first question, refer to the following portion: "In wet years rings are broad; during drought years they are narrow, since the trees grow less. Often, ring patterns of dead trees of different, but overlapping, ages can be correlated to provide an extended index of past climate conditions."

So if we look at the ring patterns of dead trees, we should be able to tell which years were dry and which years were wet based on the width of the rings. If we only have one tree, then we would obviously only be able to gather data for the years in which that tree was alive. But now imagine we have two trees. One of the trees died in 1940 at the age of 50, and the other was born in 1950 and lived for 60 years (a 10 year overlap). In that case, we would have ring data from 1890 - 2010 and could use that data to help figure out which years were wet and which were dry.

Now consider the 10-year overlap. Because we are talking about different trees, the actual widths of the rings from those years might not be exactly the same. However, during wet years, we would expect RELATIVELY broad rings. During dry years, we would expect relatively narrow rings. So even though the precise widths might not be exactly the same for both trees, the PATTERNS (i.e. narrow-narrow-broad-narrow-broad-broad-broad-etc) will likely be the same. Now the second paragraph does explain why this is not ALWAYS the case, but the passage suggests that the patterns will OFTEN exhibit similar patterns.

Hopefully that helps you arrive at the correct answer!

Quote:
2. In the highlighted text, "uncertainties" refers to
A. dendrochronologists' failure to consider the prevalence of erratic weather patterns
B. inconsistencies introduced because of changes in methodology
C. some tree species' tendency to deviate from the norm
D. the lack of detectable variation in trees with complacent rings
E. the lack of perfect correlation between the number of a tree's rings and its age

The highlighted portion specifically refers to trees that may go a year or two without adding rings. According to the first paragraph, it is often possible to determine a tree's age by counting the rings. Why? Because there is typically an annual boundary line at the end of the growing season. With a regular annual growth pattern, you can count the rings to determine the age.

But what if a tree goes a year or two without adding any rings? In that case, if you count the rings to determine the age, your number will be LESS than the tree's actual age. For example, if you count 40 rings, the tree could actually be 41, 42, 45, 50, or 60+ years old! We would have no way to determine the number of years in which rings were not added. This corresponds to choice (E).

As for choice (D), the highlighted portion refers to the uncertainty in ring count, not to the lack of variation in ring width in complacent trees. We are indeed told that trees with "complacent" rings show little variation in ring width from year to year. However, you should still be able to count rings to determine the AGE of complacent trees. You would not be able to tell which years were wet/dry, but you should still be able to determine the age.

Choice (E) is the best answer.

Hi GMATNinja,

I have 1 query regarding interpretation of the phrase overlapping ages. I understand that overlapping ages are the years in which both trees would be in existence. Whereas your explanation of question 1 suggests that overlapping ages are the years in which neither of the 2 trees exist, i.e. 1940-1950.

Can you please clarify the meaning of the word overlap in the context of the passage?

Thank you.
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Dendrochronology, the study of tree-ring records to glean information  [#permalink]

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25 Jan 2020, 23:30
Can sb tell me which one (E) (A) (C) (D) is correct??? As I saw on the forum, different person post different answer????

(A)
For the first question, refer to the following portion: "In wet years rings are broad; during drought years they are narrow, since the trees grow less. Often, ring patterns of dead trees of different, but overlapping, ages can be correlated to provide an extended index of past climate conditions."

So if we look at the ring patterns of dead trees, we should be able to tell which years were dry and which years were wet based on the width of the rings. If we only have one tree, then we would obviously only be able to gather data for the years in which that tree was alive. But now imagine we have two trees. One of the trees died in 1940 at the age of 50, and the other was born in 1950 and lived for 60 years (a 10 year overlap). In that case, we would have ring data from 1890 - 2010 and could use that data to help figure out which years were wet and which were dry.

Now consider the 10-year overlap. Because we are talking about different trees, the actual widths of the rings from those years might not be exactly the same. However, during wet years, we would expect RELATIVELY broad rings. During dry years, we would expect relatively narrow rings. So even though the precise widths might not be exactly the same for both trees, the PATTERNS (i.e. narrow-narrow-broad-narrow-broad-broad-broad-etc) will likely be the same. Now the second paragraph does explain why this is not ALWAYS the case, but the passage suggests that the patterns will OFTEN exhibit similar patterns.

A very good and detailed explanation, thanks GMATNinja
(OA) gives this one as correct answer

However if we see from the last sentence of paragraph2
Certain species sometimes add more than one ring in a single year, when growth halts temporarily and then starts again.

So shouldn’t that we also need to take into account certain “species” to determine whether they exhibit “similar pattern”?????

(C)
We can infer from sentence as below
“Certain” species sometimes add more than one ring in a single year, when growth halts temporarily and then starts again.
-not “every” species
So it’s possible that even if they were different species, maybe “the rings corresponding to the overlapping years would exhibit similar patterns.”
-hence incorrect

(D)
However, its plausible for this explanation written by desaichinmay22
I also have a way of thinking same as desaichinmay22

In the passage it is stated that often, ring patterns of dead trees of different, but overlapping, ages can be correlated to provide an extended index of past climate conditions. Start of second passage states that "complacent" rings tell nothing about changes in climate. Hence it can be deduced that rings corresponding to overlapping years couldn't be complacent rings.

So why (D) cannot be the correct answer???

Or maybe it(the rings corresponding to the overlapping years) could be “complacent” rings, but it cannot tell anything about changes in climate????

(E)
Its obviously incorrect, since from the second passage

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. And trees in extremely dry regions may go a year or two without adding any rings,

- hence we can infer that “steady wet” &“extremely dry” tell nothing about changes in climate

So (E) The rings corresponding to the overlapping years would provide a more reliable index of dry climate conditions than of wet conditions.-obviously not correct
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Re: Dendrochronology, the study of tree-ring records to glean information  [#permalink]

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26 Jan 2020, 01:00
Why (B) cannot be correct answer???
I have the same problem as zoezhuyan

we can see from the first word “however” in para2, doesn’t it indeed “ question” the validity of Dendrochronology,a method to study the tree-ring records for gleaning information about the past, in para1???

We can easily see from this passage that (C) correspond to para1’s main idea, and for (B), it correspond to para2

Or maybe we can think for another way, it is that—which one, para1 or 2, is this passage’s main focus???however, its not quite obvious in this whole passage for us to discern which one is the main focus
so in Q3, it just hard for us to choose between (B) and (C)
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Re: Dendrochronology, the study of tree-ring records to glean information  [#permalink]

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05 Feb 2020, 18:40
1
zoezhuyan wrote:
what's the problem of the B in Q3?

IMOP, P1 states general patterns of rings under different environments,
while, P2 says patterns are similar under certain environment, and under some other certain environments, pattern has "uncertain" pattern, question the accuracy of the age if count the rings.
because I think Q2 questions the patterns, so I picked up B,
I think C does not include what P2 says, so I cross off C
I saw B is the second ranking, suggesting not few people agree with B.

When answering "main idea" questions on RC, looking for the answer choice that "covers what all the paragraphs said" will cause you endless frustration and often lead you to the wrong answer choice.

That's because the question is not, "Which answer choice seems to cover the content of every paragraph?"

Rather, the question is, "Why did the author write this passage in the first place?"

mimishyu wrote:
Why (B) cannot be correct answer???
I have the same problem as zoezhuyan

we can see from the first word “however” in para2, doesn’t it indeed “ question” the validity of Dendrochronology,a method to study the tree-ring records for gleaning information about the past, in para1???

We can easily see from this passage that (C) correspond to para1’s main idea, and for (B), it correspond to para2

Or maybe we can think for another way, it is that—which one, para1 or 2, is this passage’s main focus???however, its not quite obvious in this whole passage for us to discern which one is the main focus
so in Q3, it just hard for us to choose between (B) and (C)

Again, why did the author write the passage?

• The author wrote P1 in order to introduce the technique of dendrochronology and show how this method can reveal past climate conditions.
• The author wrote P2 in order to explain a few scenarios where dendrochronology's results can be compromised. In other words, the author wrote P2 to qualify the statements made in P1, rounding out the overall explanation of how dendrochronology works.

The author wanted to explain how dendrochronology can be used to deduce climate history (including when it might not work).

Let's take a look at choice (B) one more time:

Quote:
The passage is primarily concerned with B. questioning the validity of a method used to study tree-ring records

Did the author write this passage in order to question the validity of a method?

Nope. While reading P2 in isolation might lead us to choose (B), remember that the reason the author wrote P2 in the first place is to expand on P1. None of the language here signals a desire by the author to convince us that these exceptions should make us question the validity of dendrochronology overall.

The overarching purpose is to present a well-rounded explanation of how and when it works. When it might not work is presented as part of that explanation, not a challenge to the method's validity.

That's why choice (C) is the best fit and choice (B) can be eliminated.
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Re: Dendrochronology, the study of tree-ring records to glean information   [#permalink] 05 Feb 2020, 18:40
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