The correct option is A most people in Omelas are utilitarians.
The author states that “most people stay in Omelas” after they have visited the child. This indicates that they understand and have accepted the utilitarian nature of their society. Only a few walk away and reject the society, so choice b is incorrect. The summary clearly states that everyone except the child and the ones who are “unable to bear the fact that they are responsible for the suffering of that child” are happy, so choice c is incorrect. No evidence indicates that the child willingly sacrifices himself for others (choice d). The passage makes no reference to LeGuin’s popularity or success as a science-fiction writer, so choice e is incorrect.