(A) Most Asokan inscriptions were in Prakrit language:  Asoka used Prakrit language for most of his inscriptions.

(C) Most Prakrit inscriptions of Asoka were written in Brahmi script: the majority of Asoka's Prakrit inscriptions were indeed written in the Brahmi script.

(E) Greek scripts were used for inscriptions in the northwest of the subcontinent:  Greek scripts were used in some inscriptions in the northwestern regions, particularly in the areas that came into contact with Greek culture during the reign of the Indo-Greek kings.

So,the correct option is [3].