Which of these is a real sustainability initiative implemented by a major astronomical observatory to reduce its environmental impact?

The astronomy industry faces unique environmental challenges, from the energy consumption of powerful telescopes to the carbon footprint of international research collaborations. In recent years, many observatories and space agencies have launched ambitious sustainability initiatives to reduce their environmental impact while continuing to explore the cosmos. This poll tests your knowledge about how the astronomy sector is becoming more environmentally responsible through innovative product and operational developments.

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The Vera C. Rubin Observatory in Chile using specialized mirror coatings that convert absorbed sunlight into electricity
The European Southern Observatory powering its Very Large Telescope with hydrogen fuel cells and on-site solar arrays
NASA's Hubble Space Telescope being retrofitted with biodegradable components designed to harmlessly disintegrate upon re-entry
The Mauna Kea observatories in Hawaii using cryogenic cooling systems that capture and convert atmospheric carbon dioxide