Final answer:
Xu of Xian is not associated with founding a religious ideology, unlike Siddhartha Gautama (Buddha), Zoroaster, and Abraham of Ur, who are important figures in major world religions such as Buddhism, Zoroastrianism, and Judaism.
Step-by-step explanation:
The historical figure among the provided options not associated with the founding of a religious ideology or philosophy is C. Xu of Xian. Siddhartha Gautama (Buddha), Zoroaster (Zarathustra), and Abraham of Ur are all founders or significant figures in major world religions such as Buddhism, Zoroastrianism, and Judaism, respectively. Xu of Xian is not recognized as a founder of a religion, and the mention of his name seems to be a red herring, particularly as it closely resembles the name of an ancient Greek mathematician and astronomer who has no connection to founding a religion.
The founders of Hinduism are not easily identified, as Hinduism has no single founder and is a synthesis of various beliefs and practices; however, important figures include Krishna. Siddhartha Gautama (Buddha) is the founder of Buddhism. Among the founders believed by their religion to be God in human form are Krishna in Hinduism and Jesus in Christianity. The holiest book of Islam is the Quran, not listed in the provided choices.