Detailed Solution:
The correct answer is “Bhagavata”.
The "Bhagavata" or "Bhagavata Purana" is not part of the "Prasthana Trayi". The Bhagavata Purana is a later devotional text, not considered part of the Prasthana Trayi.
Prasthana Trayi is a Sanskrit term that refers to the three primary sources of Vedanta philosophy. These are: Upanishads, Brahma Sutras and Bhagavad Gita.