Option c is the correct answer. Megasthenes ( 350 BCE - c. 290 BCE), the famous Greek ambassador, came to the court of Chandragupta Maurya. He was an ancient Greek historian, diplomat, ethnographer, and explorer. He described India in his book "Indica," which is now lost but has been partially reconstructed from later authors' quotations. Megasthenes's visit to the Mauryan court took place during the reign of Chandragupta Maurya in Pataliputra (modern Patna). He is known for being one of the first Westerners to provide a written account of India.