Answer: Community
Explanation: So a Population is a specific group of animals, such as a group of wolves, but in this pic, there are all kinds of different animals. An organism is a single living thing, like one cat by itself. An ecosystem is more like a whole forest, while a community is a single spot or area where all kinds of animals react to each other as you have prey and predator.
Ecosystem and community are very similar, but the community is a specific area, and it's smaller than the ecosystem.