A Delhi Sultanate official must send an urgent letter to a distant to…

The correct answer is Option (1) → The foot-post, with runners changed every third of a mile

Option (1) The foot-post, with runners changed every third of a mile — Correct. The foot-post, called dawa, had three stations per mile, so fresh runners took over every third of a mile. Ibn Battuta found it quicker than the horse-post.

Option (2) The horse-post, with royal horses changed every four miles — Incorrect. This is the real horse-post, called uluq, with horses stationed every four miles. But Ibn Battuta found the foot-post quicker than it.

Option (3) The horse-post, with royal horses changed every third of a mile — Incorrect. The horse-post had its stations every four miles. A third of a mile was the gap between foot-post stations, so the distance is wrongly given.

Option (4) The foot-post, with runners changed every four miles — Incorrect. Foot-post stations stood every third of a mile, three to a mile. Four miles was the gap between horse-post stations.