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jack5397
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02 Jun 2024, 03:31
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In the central Amazon basin, sediment deposits more than sixteen million years old consist of clays formed from rocks found in the basin itself. But the sediment deposits sixteen million years old or younger also include dark sand resembling rocks found in the Andes mountain range. These observations have led geologists to conclude that around sixteen million years ago, rivers in the Andes first began to drain into the central Amazon basin.
Which of the following, if true, would most strengthen the geologists' reasoning?
A) Sediment deposits more than sixteen million years old in both the Andes and the central Amazon basin contain similar types of clays.
B) Rivers in the Andes and elsewhere form sediment deposits today similar to deposits formed sixteen million years ago in the same regions.
C) The sediment deposits with dark sand contain fossilized pollen from plant species that grew only in the Andes, but the older deposits do not.
D) Rocks resembling the dark sand in the younger sediment deposits are common between the Andes and the central Amazon basin.
E) Sediment deposits less than sixteen million years old in the eastern Amazon, far from the Andes, also include the dark sand.
Which of the following, if true, would most strengthen the geologists' reasoning?
A) Sediment deposits more than sixteen million years old in both the Andes and the central Amazon basin contain similar types of clays.
B) Rivers in the Andes and elsewhere form sediment deposits today similar to deposits formed sixteen million years ago in the same regions.
C) The sediment deposits with dark sand contain fossilized pollen from plant species that grew only in the Andes, but the older deposits do not.
D) Rocks resembling the dark sand in the younger sediment deposits are common between the Andes and the central Amazon basin.
E) Sediment deposits less than sixteen million years old in the eastern Amazon, far from the Andes, also include the dark sand.
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03 Jun 2024, 20:58
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In the central Amazon basin, sediment deposits more than sixteen million years old consist of clays formed from rocks found in the basin itself. But the sediment deposits sixteen million years old or younger also include dark sand resembling rocks found in the Andes mountain range. These observations have led geologists to conclude that around sixteen million years ago, rivers in the Andes first began to drain into the central Amazon basin.
The geologists have concluded the following:
around sixteen million years ago, rivers in the Andes first began to drain into the central Amazon basin
The passage mentions some evidence that supports that conclusion:
In the central Amazon basin, sediment deposits more than sixteen million years old consist of clays formed from rocks found in the basin itself. But the sediment deposits sixteen million years old or younger also include dark sand resembling rocks found in the Andes mountain range.
We see that the reasoning of the argument is basically that, since sediments in the Amazon basin more than sixteen million years old don't contain dark sand resembling rocks from the Andes mountains whereas newer sediments do contain such dark sand, rivers in the mountains started draining in the Amazon basin around sixteen million years ago.
Which of the following, if true, would most strengthen the geologists' reasoning?
This is a Strengthen question, and the correct answer will somehow strengthen the support for the geologists' conclusion.
A) Sediment deposits more than sixteen million years old in both the Andes and the central Amazon basin contain similar types of clays.
If anything, this choice weakens, rather than strengthens, the argument.
After all, information that sediments more than sixteen million years old in the Amazon basin and the Andes are similar is reason to believe that rivers in the Andes were draining into the Amazon basin more than sixteen million years ago.
Of course, if they were draining into the basin more than sixteen million years ago, then the conclusion that they started draining into the basin sixteen million years ago would not be correct. So, if anything, this choice serves to cast a little doubt on the conclusion.
We could also argue that this choice has no effect on the argument since the passage says, "In the central Amazon basin, sediment deposits more than sixteen million years old consist of clays formed from rocks found in the basin itself." That information indicates that the clay deposits in the basin did not come from the Andes.
Either way, this choice does not strengthen the argument.
Eliminate.
B) Rivers in the Andes and elsewhere form sediment deposits today similar to deposits formed sixteen million years ago in the same regions.
This choice is a little tough to eliminate since it could seem to connect rivers in the Andes to deposits formed sixteen million years ago in the Amazon basic, but here's the thing.
Notice that this choice is not about the locations of deposits. It's about the characteristics of deposits. The point of this choice is that characteristics of deposits formed today are similar to those of deposits formed long ago.
OK, great, but did rivers in the Andes deposit sediment in the Amazon basin sixteen million years ago? This choice doesn't indicate anything about where sediment was deposited by rivers in the Andes.
Also, this choice does not indicate that deposits from rivers in the Andes today are like the black sand found in the Amazon basin. It just says that new deposits are like older ones without saying what the new deposits or the older ones are like. So, we have to be careful not to make up in our minds an unsupported story about deposits of today being similar to the black sand and thus justify this incorrect choice.
This choice has no effect on the strength of the argument.
Eliminate.
C) The sediment deposits with dark sand contain fossilized pollen from plant species that grew only in the Andes, but the older deposits do not.
This choice is a powerful strengthener.
After all, this choice provides an additional reason to believe that rivers in the Andes started draining in the Amazon basin sixteen million years ago.
After all, if the sediment deposits with the dark sand contain pollen from plants that grew only in the Andes, then we have a clear connection between the Andes and the deposits that began to exist sixteen million years ago along with the dark sand in the sediments. After all, it makes sense that, if the sediments deposits with the dark sand contain pollen from plants that grew only in the Andes, then it's quite likely that the dark sand is also from the Andes and that rivers in Andes deposited both the sand and the pollen in the Amazon basin, starting around sixteen million years ago.
Keep.
D) Rocks resembling the dark sand in the younger sediment deposits are common between the Andes and the central Amazon basin.
This choice is tricky because we might think it strengthens the argument by showing that rivers in the Andes either somehow picked up dark sand from the rocks between the Andes and the Amazon basin or deposited rocks between the Andes and the Amazon basin and that, therefore, it's true that the dark sand is from the Andes, meaning that rivers in the Andes started to drain into the Amazon sixteen million years ago.
We can eliminate this choice for a couple reasons though.
One reason is that the significance of the dark rocks is not clear. Maybe they came from the Andes. Maybe they didn't. Maybe they are the source of the sand, and maybe not, and if they are, maybe that information means that the sand didn't come from the Andes after all. So, since we don't have any of those details, the fact that the dark rocks exist doesn't have clear implications for the case for the conclusion.
The second reason is that (C) is such a powerful strengthener that we can safely eliminate this choice with its unclear implications and choose (C) instead.
Eliminate.
E) Sediment deposits less than sixteen million years old in the eastern Amazon, far from the Andes, also include the dark sand.
This choice weakens, rather than strengthens, the argument.
After all, if the dark sand can be found in areas far from the Andes, then apparently, the dark sand can come from a source other than the Andes.
In that case, it could be that some or all of the dark sand near the Andes came from another source as well.
So, given what this choice says, it could be that rivers in the Andes didn't start draining in the Amazon basin sixteen million years ago and that, actually, the reason there is dark sand in sediments less than sixteen million years old is that dark sand started coming from some source other than the Andes around sixteen million years ago.
Eliminate.
Correct answer: C
The geologists have concluded the following:
around sixteen million years ago, rivers in the Andes first began to drain into the central Amazon basin
The passage mentions some evidence that supports that conclusion:
In the central Amazon basin, sediment deposits more than sixteen million years old consist of clays formed from rocks found in the basin itself. But the sediment deposits sixteen million years old or younger also include dark sand resembling rocks found in the Andes mountain range.
We see that the reasoning of the argument is basically that, since sediments in the Amazon basin more than sixteen million years old don't contain dark sand resembling rocks from the Andes mountains whereas newer sediments do contain such dark sand, rivers in the mountains started draining in the Amazon basin around sixteen million years ago.
Which of the following, if true, would most strengthen the geologists' reasoning?
This is a Strengthen question, and the correct answer will somehow strengthen the support for the geologists' conclusion.
A) Sediment deposits more than sixteen million years old in both the Andes and the central Amazon basin contain similar types of clays.
If anything, this choice weakens, rather than strengthens, the argument.
After all, information that sediments more than sixteen million years old in the Amazon basin and the Andes are similar is reason to believe that rivers in the Andes were draining into the Amazon basin more than sixteen million years ago.
Of course, if they were draining into the basin more than sixteen million years ago, then the conclusion that they started draining into the basin sixteen million years ago would not be correct. So, if anything, this choice serves to cast a little doubt on the conclusion.
We could also argue that this choice has no effect on the argument since the passage says, "In the central Amazon basin, sediment deposits more than sixteen million years old consist of clays formed from rocks found in the basin itself." That information indicates that the clay deposits in the basin did not come from the Andes.
Either way, this choice does not strengthen the argument.
Eliminate.
B) Rivers in the Andes and elsewhere form sediment deposits today similar to deposits formed sixteen million years ago in the same regions.
This choice is a little tough to eliminate since it could seem to connect rivers in the Andes to deposits formed sixteen million years ago in the Amazon basic, but here's the thing.
Notice that this choice is not about the locations of deposits. It's about the characteristics of deposits. The point of this choice is that characteristics of deposits formed today are similar to those of deposits formed long ago.
OK, great, but did rivers in the Andes deposit sediment in the Amazon basin sixteen million years ago? This choice doesn't indicate anything about where sediment was deposited by rivers in the Andes.
Also, this choice does not indicate that deposits from rivers in the Andes today are like the black sand found in the Amazon basin. It just says that new deposits are like older ones without saying what the new deposits or the older ones are like. So, we have to be careful not to make up in our minds an unsupported story about deposits of today being similar to the black sand and thus justify this incorrect choice.
This choice has no effect on the strength of the argument.
Eliminate.
C) The sediment deposits with dark sand contain fossilized pollen from plant species that grew only in the Andes, but the older deposits do not.
This choice is a powerful strengthener.
After all, this choice provides an additional reason to believe that rivers in the Andes started draining in the Amazon basin sixteen million years ago.
After all, if the sediment deposits with the dark sand contain pollen from plants that grew only in the Andes, then we have a clear connection between the Andes and the deposits that began to exist sixteen million years ago along with the dark sand in the sediments. After all, it makes sense that, if the sediments deposits with the dark sand contain pollen from plants that grew only in the Andes, then it's quite likely that the dark sand is also from the Andes and that rivers in Andes deposited both the sand and the pollen in the Amazon basin, starting around sixteen million years ago.
Keep.
D) Rocks resembling the dark sand in the younger sediment deposits are common between the Andes and the central Amazon basin.
This choice is tricky because we might think it strengthens the argument by showing that rivers in the Andes either somehow picked up dark sand from the rocks between the Andes and the Amazon basin or deposited rocks between the Andes and the Amazon basin and that, therefore, it's true that the dark sand is from the Andes, meaning that rivers in the Andes started to drain into the Amazon sixteen million years ago.
We can eliminate this choice for a couple reasons though.
One reason is that the significance of the dark rocks is not clear. Maybe they came from the Andes. Maybe they didn't. Maybe they are the source of the sand, and maybe not, and if they are, maybe that information means that the sand didn't come from the Andes after all. So, since we don't have any of those details, the fact that the dark rocks exist doesn't have clear implications for the case for the conclusion.
The second reason is that (C) is such a powerful strengthener that we can safely eliminate this choice with its unclear implications and choose (C) instead.
Eliminate.
E) Sediment deposits less than sixteen million years old in the eastern Amazon, far from the Andes, also include the dark sand.
This choice weakens, rather than strengthens, the argument.
After all, if the dark sand can be found in areas far from the Andes, then apparently, the dark sand can come from a source other than the Andes.
In that case, it could be that some or all of the dark sand near the Andes came from another source as well.
So, given what this choice says, it could be that rivers in the Andes didn't start draining in the Amazon basin sixteen million years ago and that, actually, the reason there is dark sand in sediments less than sixteen million years old is that dark sand started coming from some source other than the Andes around sixteen million years ago.
Eliminate.
Correct answer: C
16 Jun 2025, 19:54
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To strengthen the geologists’ reasoning, we must support the conclusion that "around 16 million years ago, rivers in the Andes began to drain into the central Amazon basin".
The geologists base this conclusion on the observation that
Before 16 million years ago: only local clays (from rocks in the basin).
After 16 million years ago: clays and dark sand resembling Andean rocks.
A) Sediment deposits more than sixteen million years old in both the Andes and the central Amazon basin contain similar types of clays.
This doesn’t tell us about new Andean input after 16 million years ago.
B) Rivers in the Andes and elsewhere form sediment deposits today similar to deposits formed sixteen million years ago in the same regions.
This tells us about modern analogies, but doesn't link Andean rivers specifically to the central Amazon 16 million years ago.
C) The sediment deposits with dark sand contain fossilized pollen from plant species that grew only in the Andes, but the older deposits do not.
If pollen from Andean-only species appears only after 16 million years ago, that strongly suggests material started coming from the Andes via rivers, bolstering the claim that Andes rivers began draining into the Amazon at that time.
D) Rocks resembling the dark sand in the younger sediment deposits are common between the Andes and the central Amazon basin.
If such rocks are common between the Andes and Amazon, the dark sand could’ve come from there—not necessarily from the Andes.
E) Sediment deposits less than sixteen million years old in the eastern Amazon, far from the Andes, also include the dark sand.
This could suggest another unknown source for the dark sand, which undermines the Andes-specific conclusion.
Correct answer: C
The geologists base this conclusion on the observation that
Before 16 million years ago: only local clays (from rocks in the basin).
After 16 million years ago: clays and dark sand resembling Andean rocks.
A) Sediment deposits more than sixteen million years old in both the Andes and the central Amazon basin contain similar types of clays.
This doesn’t tell us about new Andean input after 16 million years ago.
B) Rivers in the Andes and elsewhere form sediment deposits today similar to deposits formed sixteen million years ago in the same regions.
This tells us about modern analogies, but doesn't link Andean rivers specifically to the central Amazon 16 million years ago.
C) The sediment deposits with dark sand contain fossilized pollen from plant species that grew only in the Andes, but the older deposits do not.
If pollen from Andean-only species appears only after 16 million years ago, that strongly suggests material started coming from the Andes via rivers, bolstering the claim that Andes rivers began draining into the Amazon at that time.
D) Rocks resembling the dark sand in the younger sediment deposits are common between the Andes and the central Amazon basin.
If such rocks are common between the Andes and Amazon, the dark sand could’ve come from there—not necessarily from the Andes.
E) Sediment deposits less than sixteen million years old in the eastern Amazon, far from the Andes, also include the dark sand.
This could suggest another unknown source for the dark sand, which undermines the Andes-specific conclusion.
Correct answer: C
