The author of Rajaniti Ratnakara is

The correct answer is C. Jyotiresvara.

Rajaniti Ratnakara is a Sanskrit treatise on statecraft written by Jyotiresvara in the 12th century. It is one of the most important works on Indian political thought. The treatise covers a wide range of topics, including the nature of kingship, the duties of a king, the art of war, and the administration of justice.

Jyotiresvara was a minister in the court of the Chola king Kulothunga Chola I. He was a scholar and a poet, and he is also known for his work on the Hindu law code, the Dharmashastra.

The other options are incorrect.

• Chandesvara was a 12th-century Indian poet and philosopher. He is best known for his work on the Advaita Vedanta philosophy.
• Vidyapati was a 14th-century Indian poet and musician. He is best known for his work in the Maithili language.
• Haribrahmendra was a 13th-century Indian saint and philosopher. He is best known for his work on the Dvaita Vedanta philosophy.