Ashoka, the Mauryan emperor, is known for inscribing his edicts on pillars and rocks throughout his empire. The use of multiple scripts, including Aramaic and Greek, was aimed at spreading his messages to a diverse population within his vast empire.

The specific use of Aramaic and Greek scripts was more prominent in the northwestern part of his empire, which included regions corresponding to present-day Afghanistan and Pakistan. These scripts were likely chosen to communicate with the diverse populations and cultures in those areas, where different languages and writing systems were in use.

So, the correct option is [3].