The correct answer is: A. Krishnadasa Kaviraja.
Krishnadasa Kaviraja was a 16th-century Bengali poet and saint who wrote the Chaitanya Charitamrita, a biography of the 16th-century Indian saint Chaitanya Mahaprabhu. The Chaitanya Charitamrita is considered to be one of the most important texts in the Vaishnava tradition.
Namadeva was a 13th-century Marathi poet and saint who is considered to be one of the founders of the Varkari sect of Hinduism. Namadeva’s poetry is known for its simple language and its devotional themes.
Shankar Dev was a 16th-century Assamese poet and saint who is considered to be one of the founders of the Vaishnava tradition in Assam. Shankar Dev’s poetry is known for its use of Assamese language and its devotional themes.
Therefore, the correct answer is A. Krishnadasa Kaviraja.