The correct answer is A.
Nirguna saints are those who believe in a formless God, which has no attributes or qualities. They believe that God is beyond all names and forms, and can only be apprehended through inner (mystical) experience.
Option A is not the advocacy of Nirguna saints because it advocates the worship of the anthropomorphic manifestations of the divine being, particularly Rama and Krishna. Nirguna saints believe that God is beyond all forms, and that to worship any form of God is to limit God.
Option B is the advocacy of Nirguna saints because it describes the concept of a formless God, which has no attributes or qualities.
Option C is the advocacy of Nirguna saints because it describes the concept of Ishvara, the personal and purely spiritual aspect of godhead, beyond all names and forms (nama-rupa), and is to be apprehended only by inner (mystical) experience.
Option D is not an option because it is not a statement about the advocacy of Nirguna saints.