Answer:
C. Soldiers
Step-by-step explanation:
The Roman road system was actually created for military purposes - meaning, they were built to ease the travel of soldiers and generals throughout the empire. That makes C correct.
Artists didn't travel so extensively throughout the empire as soldiers did, so they didn't benefit as much. Engineers were the ones who built the system. Priests, like artists, did not have a need to move around too much, remaining mostly at the church, so this is wrong as well.