The correct answer is: A. Adi Shankaracharya.
Adi Shankaracharya was a Hindu philosopher and theologian who lived in the 8th century CE. He is considered one of the most important figures in Hindu philosophy and is credited with reviving the Advaita Vedanta school of thought. Advaita Vedanta is a non-dualistic philosophy that teaches that Brahman, the ultimate reality, is the only thing that exists. Everything else, including the individual self, is an illusion.
Surdas was a 16th-century Indian poet and saint who is considered one of the greatest composers of devotional songs in the Braj language. He is also known for his hymns to Krishna, which are still widely sung today.
Ramanuja was a 12th-century Indian philosopher and theologian who is considered one of the founders of the Visistadvaita school of thought. Visistadvaita is a qualified non-dualistic philosophy that teaches that Brahman is the ultimate reality, but that the individual self is also real, although it is dependent on Brahman.
Kapila was a 6th-century BCE Indian philosopher who is considered the founder of the Samkhya school of thought. Samkhya is a dualistic philosophy that teaches that there are two fundamental realities: Purusha, the conscious principle, and Prakriti, the material principle.