Paragraph Completion Practice

Paragraph Completion 15 / 53

The increasing atmospheric concentration of anthropogenic carbon dioxide, primarily from fossil fuel combustion, is a principal driver not only of global warming but also of a less recognized yet equally pervasive environmental crisis: ocean acidification. As the oceans absorb a significant portion of this excess CO2, a chemical reaction occurs that forms carbonic acid, consequently lowering the pH of seawater and altering its carbonate chemistry. This fundamental change directly imperils marine ecosystems, particularly those reliant on calcification for structural integrity, such as coral reefs and shellfish, with cascading effects throughout the food web.

Which of the following sentences best completes this paragraph?

A. Such widespread biological distress mandates an urgent, comprehensive global strategy to reduce carbon emissions and mitigate the irreversible degradation of marine biodiversity.
B. However, some researchers suggest that certain marine organisms may possess adaptive capabilities that could help them cope with these changing conditions.
C. This phenomenon has also been linked to changes in primary productivity in certain oceanic regions, further complicating ecological models.
D. The economic consequences of diminished fisheries and disrupted coastal protection are projected to be substantial for many island nations.

Correct Answer: A
Why A works: The paragraph establishes ocean acidification as a profound environmental crisis, detailing its cause (anthropogenic CO2), mechanism (pH reduction), and significant ecological consequences (threat to calcifying organisms and food webs). Option A serves as an excellent capstone by synthesizing these points into a clear call for action, linking the biological distress directly to the need for carbon emission reduction and global mitigation efforts, thus concluding the argument with a comprehensive and policy-oriented implication.
Why B fails: Option B introduces a potential nuance (adaptive capabilities) that shifts the focus away from the established crisis and its broad implications, potentially offering a counter-argument or a point of scientific uncertainty rather than a conclusive statement on the problem's gravity or the necessary response. It does not provide a strong, overarching conclusion to the paragraph's argument about the widespread biological distress.
Why C fails: Option C introduces a specific, albeit related, scientific detail (changes in primary productivity and ecological models). While relevant to oceanography, it narrows the scope considerably from the broad ecological crisis and its implications discussed in the paragraph, failing to provide a comprehensive concluding statement that summarizes the overarching problem or its required solution.
Why D fails: Option D focuses exclusively on the economic consequences for a specific group (island nations) and a particular sector (fisheries). This is too narrow in scope, as the paragraph emphasizes broader ecological damage and cascading food web effects, which imply much wider and more fundamental impacts than just economics for specific regions. It does not encompass the full breadth of the crisis established.

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