While talking to her coworker Binai, Corrine learns her coworker graduated from the same university as she did. Corrine had previously thought that Binai and she had nothing in common since Binai was from India originally and Corrine is American. Corrine and Binai formed a connection because they both went to the same university. The theory that attempts to explain why people define themselves by groups is known as: A. Self-enhancement. B. Social Self. C. Attachment. D. Social Identity. E. Self-concept.