Which of the following is not an international requirement for a nation-state to be recognized?

The case of brown v. board of education was started when a. oliver brown's daughter had to walk 21 blocks to the nearest school when an all-white school was only 7 blocks away. b. oliver brown's son was caught at a sit-in at the local school district. c. oliver brown's son was unable to participate in the school's all-white football team. d. oliver brown's daughter was unable to attend high school because there were none for her to attend.