D. Cooperative

Just as the name describes, a cooperative is a group of people who have decided to cooperate or work together in order to be more efficient or effective.  Cooperatives are owned by and formed for the benefit of their members.  Members typically have a common need and have agreed to a joint strategy for addressing that need.  However, members also bear a lot of responsibility for making sure the cooperative works, with each member having an equal vote, if one member shirks his or her duties, all suffer.