Explanation:

- Sharngadeva: He is the correct answer. Sharngadeva was a 13th-century Indian musicologist known for his seminal work, the "Sangita Ratnakara," which is a comprehensive treatise on music and dance. It remains one of the most important texts in Indian classical music, detailing the musical theories of both Hindustani and Carnatic traditions.

- Lochan Kavi: He was an Indian scholar known for his contributions to classical music, but he did not author the "Sangita Ratnakara." Instead, he wrote the "Raga Tattva Vibodha" in the 17th century, a treatise on the theory of ragas.

- Jaidev: An eminent poet known for the "Gita Govinda," Jaidev’s contributions are in the field of devotional poetry and not related to the "Sangita Ratnakara."

- Ramamatya: A 16th-century musicologist, Ramamatya is known for his work "Svaramelakalanidhi," a treatise that focuses on the musical scales and modal structures of Indian classical music.

Correct Answer: Sharngadeva