An area's vegetation is highly dependent on the area's Topography
Wildlife
Inhabitants
Climate

An area's vegetation is highly dependent on the area's climate.

Explanation:

Topography; is not correct because despite its influence it is not the detrimental factor as to what type of vegetation will grow where.

Wildlife; is not correct because the wildlife depends on the type of vegetation, not the other way around.

Inhabitants; is not correct because the people may or may not influence an area's vegetation, but at the end of the day they can not replace it vegetation that can not prosper in the given conditions.

Climate; is correct because the climate is the most important factor that determines how would the vegetation be distributed around the world, and this can easily be seen by the types of vegetation in correlation with the climate zones.