Question

Your school campus, including the buildings, grounds, students, and all other organisms living there, could be considered a/an ___ .

Answer 1

An ecosystem comprises of biotic and abiotic components and their interaction within and with the physical environment. The college campus includes all abiotic components in the form of buildings, light, soil,etc and living organisms and interaction occur within the components and with the environment. Therefore, it can be called an ecosystem.
Population is just the number of all organisms that occupy a particular area and community is an assemblage of two or more populations occupying the same geographical area. Biosphere includes the whole earth so the correct answer would be ecosystem.