Answer: D. All of the choices are correct.
Explanation: A group is a collection or combination of people or organizations or items. A group can be a constructed reality,it can also be used to describe things that are not tangible,a group is also a clear application of Thomas Theorem.
Thomas theorem was formulated in the year 1928 it states that "If men define situations as real, they are real in their consequences". It can be stated as if a group of men define situations as real,they are real in their consequences.