Which term describes the zone of Earth where life naturally occurs?

The term that describes the zone of Earth where life naturally occurs is "Biosphere." This concept encompasses all living organisms on Earth, including plants, animals, and microorganisms, along with the environments that support them. The biosphere integrates with various other systems, such as the atmosphere (the layer of gases surrounding Earth), the hydrosphere (the water features of Earth, including oceans, rivers, and lakes), and the geosphere (the solid Earth, including rocks and soil).

Understanding the biosphere is crucial as it signifies the interplay between life and its environments, highlighting how organisms interact with each other and their surroundings. This term captures the entirety of regions in Earth's surface, atmosphere, and oceans where life exists, making it distinct from the other options given in the question.