Which Bhakti saint preached the concept of Vishishtadvaita?

Answer: Option B

Ramanuja, the main proponent of Vishishtadvaita philosophy contends that the Prasthanatrayi ("The three courses"), namely the Upanishads, the Bhagavad Gita, and the Brahma Sutras are to be interpreted in a way that shows this unity in diversity, for any other way would violate their consistency. Vedanta Desika defines Vishishtadvaita using the statement, Asesha Chit-Achit Prakaaram Brahmaikameva Tatvam : Brahman, as qualified by the sentient and insentient modes (or attributes), is the only reality.