Single correct option
Passage: Coral reefs occupy less than one percent of the ocean floor yet support roughly a quarter of all known marine species, a disproportion that stems from the physical complexity of reef structures, which create countless micro-habitats, and from the symbiotic relationship between coral polyps and the algae living in their tissue, which converts sunlight into the energy base of an otherwise nutrient-poor tropical ocean.
- A. Coral reefs are the largest ecosystems in the ocean by surface area.
- B. Marine biodiversity is evenly distributed across all ocean floor habitats.
- C. Coral reefs support disproportionate marine biodiversity because their structural complexity and coral-algae symbiosis sustain rich habitats despite covering little area.
- D. Algae are more important to ocean ecosystems than coral polyps.
Show answer and solution
Answer: (C) Coral reefs support disproportionate marine biodiversity because their structural complexity and coral-algae symbiosis sustain rich habitats despite covering little area.
The passage explains a disproportion (tiny area, huge biodiversity share) and gives two causes: structural complexity and coral-algae symbiosis providing energy. Option (C) captures the disproportion and both causes. (A) contradicts 'less than one percent'; (B) contradicts the entire point of disproportion; (D) invents a ranking the passage never makes, since the relationship is described as symbiotic, not hierarchical.
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