Explanation for Question 11. It can be inferred from the passage that the northern woodlands would be more likely to function as a carbon source if which of the following were to occur?Key to getting this question correct is being clear about what it's asking. The passage is focused on woodlands being a carbon sink, but this question is about the woodlands being more like to function as a carbon source. So, we have to be sure keep which one the question is about straight.
A. Vegetation regrowing on land from which trees had been cleared grew back fast enough to absorb as much CO2 as was released by deforestation.Absorbing CO2 would not result in the the woodlands being a carbon source.
Eliminate.
B. Debris from the forest floor rotted less quickly after the rate of tree growth increased.According to the passage, "deforestation releases CO2, because debris from the forest floor rots more quickly." So, debris rotting "more quickly" results in woodlands releasing CO2 or being a carbon source.
However, this choice is about the opposite, debris rotting "less quickly."
Eliminate.
C. A significant increase in the number of pests that destroy trees caused an increase in tree loss.According to the passage, "deforestation releases CO2."
So, since "tree loss" is the same as deforestation, we would expect "a significant increase in the number of pests that destroy trees" to cause an increase in release of CO2, in other words, to cause the woodlands to be "more likely to function as a carbon source."
Keep.
D. Pollution resulting from burning fossil fuels provided trees with extra nutrients, thus increasing the rate of their growth.Scanning the passage for "tree growth," we find the following:
the steep increase in tree growth rates surpassed the losses stemming from fire and logging, turning the northern forests from a carbon source into a carbon sink
So, increased tree growth would result in the woodlands being less, rather than more, likely to function as a carbon source.
Eliminate.
E. A decrease in temperature caused a significant decrease in the number of fires in the northern woodlands.Scanning the passage for "fires," we find the following:
northern woodlands were a source of CO, mainly because of forest fires
So, fires cause the woodlands to be a source of CO2.
Thus, a "decrease in the number of fires" would result in the woodlands being less, rather than more, likely to function as a carbon source.
Eliminate.
The correct answer is (C).
Explanation for Question 22. The passage is primarily concerned withA. refuting a claim about the causes of a phenomenonThe passage does not refute any claim about causes. The only claim mentioned is Allen Auclair's claim, and the passage explains rather than refutes that claim.
Eliminate
B. presenting an analysis of a common natural processThis choice is a little tough to eliminate, but we can eliminate it because it doesn't quite capture what the passage does.
The passage does mention some natural processes, but it doesn't primarily "present an analysis" of one of them. In fact, the passage doesn't really present an analysis of any process.
Rather, it mentions those processes in order to present an explanation for the fact that "the amount of CO2 produced in that time by burning fossil fuels should have resulted in a much greater increase than has been observed."
Eliminate.
C. providing an explanation for a puzzling phenomenonThis is exactly what the passage does.
It first presents a puzzling phenomenon: "the amount of CO2 produced in that time by burning fossil fuels should have resulted in a much greater increase than has been observed."
The it presents Allen Auclair's explanation for that phenomenon.
Keep.
D. evaluating the methodology used in a recent studyThe passage does not evaluate or even mention the methodology used in any study.
Eliminate.
E. contrasting two explanations of an unexpected phenomenonThis choice is half correct since the passage does discuss an explanation of what could be considered "an unexpected phenomenon," which is that "the amount of CO2 produced in that time by burning fossil fuels should have resulted in a much greater increase than has been observed."
However, since the passage presents only one explanation and is not "contrasting two explanations," this choice is incorrect.
Eliminate.
The correct answer is (C).
Explanation for Question 33. It can be inferred from the passage that Auclair's claim about carbon and the northern woodlands would be most seriously undermined if which of the following were true?A. The northern woodlands functioned as a carbon source rather than as a carbon sink prior to 1890.Scanning the passage for "1890," we find the following:
Auclair's analysis of the past hundred years shows the woodlands changing from a carbon source to a carbon sink. Before 1890, northern woodlands were a source of CO, mainly because of forest fires and logging.
We see that the idea that the northern woodlands functioned as a carbon source rather than as a carbon sink prior to 1890 is in line with what Auclair says.
Eliminate.
B. The rate of tree growth in the northern woodlands increased throughout the twentieth century.Scanning the passage for "the twentieth century," we find the following part of Auclair's explanation:
increases in the growth rates of individual trees in these forests since 1920 have created a large volume of wood that accounts for the missing carbon
Since "increases in the growth rates of individual trees in these forests since 1920" is basically the same as "The rate of tree growth in the northern woodlands increased throughout the twentieth century," what this choice says is in line with Auclair's explanation.
Eliminate.
C. The northern woodlands absorbed larger amounts of carbon after 1920 than they had in previous years.Scanning the passage for "1920," we find the following part of Auclair's explanation:
increases in the growth rates of individual trees in these forests since 1920 have created a large volume of wood that accounts for the missing carbon
So, this choice is in line with Auclair's explanation.
Eliminate.
D. During the twentieth century, the total volumes of wood lost to rot or fire in the northern woodlands exceeded increases in wood volume.Auclair's explanation involves the following:
increases in the growth rates of individual trees in these forests since 1920 have created a large volume of wood that accounts for the missing carbon
We see that his explanation requires that, "after 1920," in other words, during the 20th century, the volume of wood in the northern woodlands increased. For that outcome to have occurred, the rate of wood creation must have "surpassed" the rate of wood destruction.
So, if "volumes of wood lost to rot or fire in the northern woodlands exceeded increases in wood volume," then the volume of wood decreased, and Auclair's explanation doesn't make sense.
Keep.
E. The northern woodlands lost trees to forest fires and logging in the early twentieth century.Auclair's explanation does not require that the northern woodlands did not lose any trees to forest fires and logging. Rather, the passage says of his explanation, "After 1920,
the steep increase in tree growth rates surpassed the losses stemming from fire and logging, turning the northern forests from a carbon source into a carbon sink."
So, trees were lost to fires and logging, but tree growth rates surpassed those losses.
So, what this choice says is in line with Auclair's explanation.
Eliminate.
The correct answer is (D).