Question

which study below focuses on the biosphere?
a study measuring how human habitation has changed then population size of caribou in a decade
a study measuring how introducing wolves into an area affects the deer population
a study measuring how acidification of the oceans affects aquatic and terrestrial organisms
a study measuring how building a dam affects plants and animal populations in an area

Explanation:

The biosphere is the global sum of all ecosystems. The study on ocean acidification affecting both aquatic and terrestrial organisms is on a global - scale ecosystem level. The other studies are on a more local or regional scale (e.g., population size change due to human habitation in a decade is local, introducing wolves in an area is local, building a dam in an area is local).

Answer:

a study measuring how acidification of the oceans affects aquatic and terrestrial organisms