Option a is the correct answer. Panini: He was a Sanskrit grammarian who wrote the Ashtadhyayi, a treatise on Sanskrit grammar and linguistics. It is considered the most comprehensive and scientific work on the subject, and the foundation of classical Sanskrit. He lived around the fourth century BCE, probably in Gandhara or Taxila. Vatsyayana: He was a Sanskrit philosopher who wrote the Kamasutra, a manual on erotic love and sexuality. It is one of the oldest and most influential texts on the topic, and contains about 1250 verses divided into seven books. He lived between the second and third centuries CE, probably in Pataliputra or Benares. Chanakya: He was a statesman and philosopher who wrote the Arthashastra, a treatise on polity, economics, and statecraft. It is a comprehensive and practical guide for rulers and administrators, covering topics such as diplomacy, war, law, taxation, espionage, and welfare. Kalhana: He was a Kashmiri historian and poet who wrote the Rajatarangini, a chronicle of the kings of Kashmir from ancient times to the 12th century CE. It is regarded as the first historical work in Sanskrit literature, and contains valuable information about the political, social, and cultural history of Kashmir.