|Question 12Verbal

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Soil thawing in Alaska has been accelerating as a result of climate changes, potentially enabling increased carbon dioxide (CO₂) absorption through greater productivity of arctic bramble (Rubus arcticus) plants and other vegetation, but also potentially enabling increased CO₂ output through greater heterotrophic respiration (CO₂ generated by the activity of soil microorganisms). Hydrologist Yonghong Yi and her colleagues developed a model incorporating numerous inputs—years of soil temperature and snow cover data among them—to evaluate the effects of climate changes on the CO₂ balance in Alaska, concluding that net CO₂ is likely to increase if seasonal snow cover arrives earlier relative to the onset of soil surface freezing.
Which finding, if true, would most directly support the researchers' conclusion?
The effect of soil temperature on the growth of vegetation and on the rate of heterotrophic respiration is stronger during the period of seasonal snow cover than during the period without snow cover.
A
Relatively early snow cover reduces the amount of soil moisture available for the growth of plant species such as R. arcticus and lowers the rate of heterotrophic respiration.
B
Seasonal snow cover tends to persist longer in areas of relatively low vegetation growth and high heterotrophic respiration than in areas of relatively high vegetation growth and low heterotrophic respiration.
C
The soil insulation provided by snow cover enables heterotrophic respiration to continue during a period in which plant species such as R. arcticus are typically not growing.
D