biosphere

保护生物圈对维持地球生命至关重要。

Protecting the ___biosphere is essential for sustaining life on Earth.

科学家们正在研究如何在地球上建立一个封闭的生物圈来测试长期太空生存的可能性。

Scientists are studying how to build a closed ___biosphere on Earth to test the possibility of long-term space survival.