What term refers to communities that remain unchanged for long observable periods of time?
a) successive communities
b) stable communities
c) climax communities
d) secondary communities

The right option is; C) Climax communities

Explanation:

Climax communities are communities of organisms (plants, animals and fungi) that have reached a steady stage and remain stable with each other and their environment for a long period of time. A climax community is the last stage of ecological succession which remains relatively stable until affected by a disturbing event such as fire. Tundra, deciduous, coniferous, and tropical rain forests are examples of climax communities.

bacterium is not correct

what are the options? add them, then i will be glad to .