Option d is the correct answer. The Ashokan inscriptions in the northwestern part of the Mauryan Empire, near Peshawar, were written in the Kharosthi script. The Kharosthi script was an ancient script used in the northwestern regions of the Indian subcontinent, including present-day Pakistan and Afghanistan. It was introduced around the 3rd century BCE and remained in use until around the 3rd century CE. The inscriptions in this script provide valuable historical and linguistic insights into the region's cultural and political context during that time.