The Buddhist texts known as Pitakas were composed in the language known as Pali. Pali is a Middle Indo-Aryan language that originated in ancient India. It is considered to be a canonical language in Theravada Buddhism, which is the oldest surviving school of Buddhism.

Option 1: Sanskrit is not the correct answer because although Sanskrit is closely related to Pali and was also a prominent language in ancient India, the Buddhist texts were not composed in Sanskrit.

Option 2: Ardhamagadhi is also not the correct answer because although it was a common language in ancient India, it was not the language used to compose the Buddhist texts.

Option 4: Prakrit is not the correct answer either because, although Prakrit was widely spoken in ancient India, it was not the language used for the Buddhist texts.

Therefore, the correct answer is option 3, Pali.