The correct option is D To know the distance during travelling
Kos Minars or Mile Pillars are medieval milestones that were made by the 16th-century Afghan Ruler Sher Shah Suri and later on by Mughal emperors. They were erected to serve as markers of distance along royal routes from Agra to Ajmer, Agra to Lahore, and from Agra to Mandu in the south. They were an important part of communication and travel in a large empire.