We have to consider that animals, plants and other organisms can share specific places where they live, and where they can find different resources, such as food, couples, and space to rest. Depending on the climate of those specific areas, there would be a specific fauna and flora in those areas that can be known as ecosystems.
The greater the category and the amount of different species and particular climatic conditions, then the greater the classification would be, for example, we could classify organisms coming from biosphere (great areas of specific climatic conditions), to a only organism.
We can say then that a community consists of a group of different species populations (group of individuals that share a specific distribution), so the correct answer would be the second one: "B. All of the different population of species in one geographic area", as we can see in the picture below.