All the populations of different organisms living in the same area make up a _ A. niche
B. ecosystem
C. community
D. habitat

The answer is c a community because a

niche is the way that an organism fits into an ecosystem.
A community is when all the populations that live and interact in the same environment .

Ecosystem is all the communities that live together with the abiotic factors in the same environment.

And a habitat is where a particular organism lives.

When plants die fungi breaks them down