Read the passage: 'The coral reef ecosystem supports thousands of species, yet it covers less than one percent of the ocean floor. Rising water temperatures have caused widespread bleaching, threatening this biodiversity hotspot.' What is the primary concern expressed in this passage?
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A
Coral reefs cover too little of the ocean floor
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B
Rising temperatures threaten coral reef biodiversity
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C
Thousands of species live in the ocean
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D
Bleaching makes coral reefs more colorful