The correct answer is: a) Nagarjuna.
Nagarjuna was a Buddhist monk and philosopher who lived in the 2nd century CE. He is considered to be one of the most important figures in the development of Mahayana Buddhism. Nagarjuna is best known for his work on the Madhyamaka philosophy, which emphasizes the emptiness of all phenomena.
Asvaghosa was a Buddhist monk and poet who lived in the 1st century CE. He is best known for his work on the Buddhacarita, a biography of the Buddha.
Aryadeva was a Buddhist monk and philosopher who lived in the 4th century CE. He is a student of Nagarjuna and is considered to be one of the most important figures in the development of Madhyamaka philosophy.
Buddhaghosa was a Buddhist monk and scholar who lived in the 5th century CE. He is best known for his work on the Visuddhimagga, a comprehensive guide to Buddhist doctrine.
Nagarjuna is the most likely answer to the question because he is the only one of the four figures who is known to have lived at Nagarjunakonda in the 2nd century CE. Asvaghosa lived in the 1st century CE, Aryadeva lived in the 4th century CE, and Buddhaghosa lived in the 5th century CE.