Option d is the correct answer. Sankara's philosophy is called Advaita Vedanta, which means non-dualistic Vedanta. Advaita Vedanta holds that the ultimate reality is Brahman, which is identical to the self (atman). Advaita Vedanta aims to achieve liberation (moksha) by realizing one's true nature as Brahman, and overcoming ignorance (avidya) and illusion (maya).