Which of the Following Events Illustrates How the Suprasystem Affects

Which of the following events illustrates how the suprasystem affects a community as a system?

A) A group of concerned citizens points out the rising number of homeless persons in the community.
B) A subgroup of the community demands that housing for homeless persons be built.
C) Homeless persons decide to picket in front of the city government building.
D) The state legislature passes a law that all communities must build some housing for homeless persons.