The correct answer is option A, that is, parts of all the communities are constantly going through succession.
The ecological succession refers to the procedure of variation in the composition of the species in an ecological community with time. The time scale can be of millions of years due to a mass extinction or can be of decades due to a wildfire.
According to ecological succession, nothing stays static and habitats are changing continuously. There are two main kinds of succession, that is, primary and secondary.