The correct option is A Biosphere
Biosphere is biologically inhabited part of earth along with its physical environment consisting of lower atmosphere, land and water bodies.
Biome is a large regional unit delimited by a specific climatic zone, having a particular major vegetation zone and its associated fauna eg tundra desert, ocean etc.
Ecotone is the transition zone between two communities, e.g., forest and grassland.
Biota is a general term, which refers to living organisms.