The correct option is A Pali
After attaining enlightenment Buddha gave his first sermon at Sarnath near Varanasi. He gave his teachings to people in their own language. During that time Pali was the language that was used by the common man. So, later on, the doctrine of Buddhism was written in Pali language but with the rise of Mahayana sects, this religion started to use the Sanskrit language to educate the people.