Read the passage and mark the letter A, B, C, or D on your answer sheet to indicate the best answer to each of the following questions from...

Read the passage and mark the letter A, B, C, or D on your answer sheet to indicate the best answer to each of the following questions from 20 to 29.

Climate change deniers often propagate the argument that rising CO2 levels are beneficial, fostering plant growth and a “greener” Earth that will absorb more emissions. Their reasoning cites an observable, if incomplete, fact: for many decades, the Earth’s terrestrial ecosystems have indeed been flourishing. [I] Forests and grasslands have acted as a vast carbon sink, sequestering prodigious quantities of CO2 from the atmosphere and ameliorating the full brunt of fossil fuel use.

The discovery of this net carbon absorption in the 1960s came as a profound surprise to ecologists. Standard models had long presumed a state of equilibrium, theorizing that any CO2 uptake from growth would be rapidly nullified by decomposition and burning. [II] “There shouldn’t be sinks. Everything that grows, dies,” explains atmospheric scientist Scott Denning. Yet, this unexpected planetary boon has proven indispensable. It has historically removed between a quarter and a third of all human-generated CO2 emissions annually, providing a crucial climate buffer that has effectively slowed the pace of global warming.

The critical flaw in the denialist reasoning is the fallacious assumption that the land sink’s capacity is permanent. Scientists have long warned that ecological shocks from climate change, combined with Earth’s physical limits, would eventually cause the sink to saturate sometime this century. [III] Worryingly, new data indicate the saturation point may be arriving far sooner than any model anticipated. Alarming measurements from 2023 and 2024 reveal that the land carbon sink has, for this period, almost completely dissipated, failing to absorb its usual share of emissions.

The abrupt collapse of one of the planet’s most vital climate regulators has sent shockwaves through the scientific community. Researchers are now intensively scrutinizing data from disparate environments, from Arctic tundra to tropical rainforests. The goal is to understand the intricate mechanisms governing this precarious equilibrium. [IV] The exigent questions are whether the recent collapse is a transient anomaly or the harbinger of a permanent, irreversible shift. The scientific community must now race to determine if this is the end of Earth’s land carbon sink, and what, if anything, can be done to bolster it.

Question 20: According to paragraph 1, the observed flourishing of Earth’s terrestrial ecosystems has had the effect of ______.

A. fostering the growth of a “greener” Earth that will absorb more emissions
B. proving that rising CO2 levels are beneficial for fostering plant growth
C. citing an observable, if incomplete, fact to support a popular argument
D. lessening the total atmospheric harm caused by human fossil fuel consumption