Which threats are listed as impacting the Great Barrier Reef?

• A. Overfishing, climate change, and oil pollution
• B. Deforestation, soil erosion, and urban runoff
• C. Invasive species and volcanic activity
• D. Industrial air pollution only

Answer: (A)

The main idea being tested is which threats are widely recognized as impacting the Great Barrier Reef. Overfishing disrupts the balance of the reef ecosystem by removing important fish that keep algae in check and help control reef disease, which can allow algae to dominate and hinder coral recovery. Climate change stands out as a major danger because warming ocean temperatures cause coral bleaching, and higher CO2 levels make seawater more acidic, weakening coral skeletons and slowing growth. Oil pollution adds toxic stress to corals and other marine life, harming respiration, reproduction, and overall health, and spills can smother reef organisms. These factors together reflect the combination most commonly listed as threats to the reef. The other options mix in issues that are not the primary, direct threats to the GBR in standard assessments—deforestation and urban runoff contribute to sediment and nutrient loading but aren’t framed here as the principal trio; invasive species and volcanic activity aren’t the main drivers for this ecosystem; and industrial air pollution alone doesn’t capture the breadth of impacts the reef faces.