The correct answer is: C. Pali
Pali is a Middle Indo-Aryan language that was used as a vernacular language in the Magadha region of India during the Buddha’s lifetime. It is the language of the Theravada Buddhist canon, and is still used in Buddhist ceremonies and rituals today.
Sanskrit is an ancient Indo-Aryan language that was used as a liturgical language in Hinduism and Buddhism. It is a highly inflected language with a complex grammar.
Prakrit is a group of Middle Indo-Aryan languages that were spoken in India during the Buddha’s lifetime. They are closely related to Sanskrit, but are less inflected and have a simpler grammar.
Sauraseni is a Prakrit language that was spoken in the Saurashtra region of India. It is the language of the Jaina canon, and is still used in Jain ceremonies and rituals today.
Pali is the most likely language to have been used for the propagation of Buddhism because it was the vernacular language of the Buddha’s time and place. It is also a relatively simple language, which would have made it easier for people to learn and understand.