Concept:The biosphere is the global region around the Earth where all living organisms exist and perform their life activities.
Explanation:The biosphere is the highest level of ecological organization, covering the atmosphere, hydrosphere, and lithosphere wherever life is present.
It extends from the deepest ocean trenches to the highest atmospheric layers that support living things.
The lithosphere refers only to the solid rocky outer shell of the Earth, so it does not represent the whole zone of life.
A habitat is a narrow, local area where a particular organism or population lives, such as a pond or a savanna.
An ecosystem is a smaller unit in which living organisms interact with each other and with their non-living surroundings within a defined space.
Hence, the broad area around the Earth where life activities go on is best known as the biosphere.
Answer:A. biosphere