Solution:Nathamuni (c. 823–951 CE) was the earliest, known for compiling the Nalayira Divya Prabandham and authoring Nyayatattva, establishing the Sri Vaishnava foundation.Yamunacharya (c. 917–1032 CE), Nathamuni's grandson-disciple, laid philosophical groundwork with works like Siddhitraya, preceding Ramanuja as his guru.
Ramanuja (1017–1137 CE) systematized Vishishtadvaita through Sri Bhashya, building directly on his predecessors Yamunacharya and Nathamuni.
Vedanta Desika (1268–1369 CE) came last as a post-Ramanuja acharya, authoring polemical works and leading the Vadakalai sub-school.
Note on Options: The provided choices (a–d) appear mismatched to the query format (no explicit labeling like A=1, B=2), likely a copy-paste error from prior MCQs. The sequence is 2 → 4 → 1 → 3 if numbered as listed (Ramanuja=1, Nathamuni=2, etc.)