Which of the Following Examples Best Describes an Ecological Community

Which of the following examples best describes an ecological community?

A) The intraspecific competition of members of a brook trout population inhabiting a stream during a given year.
B) The interactions of all the plant and animal species inhabiting a 2 hectare forest.
C) The material cycling and energy transformations between the biotic and abiotic components of an open meadow.
D) The various species of barnacles competing for resources in an intertidal zone.
E) The interactions of the various plant and animal species of park, excepting the decomposers.