Answer:
B. post roads
Explanation:
The highways build by Darius head to the Persian Empire, were an excellent communication system from which a Royal Road allowed economical activities, politicians, and people to travel widely across on of the largest Empires.
The Royal Road made possible communication to rules of a vast empire like Persia.
Royal Road allowed the king to send orders to and receive information from everywhere relatively quickly.
Empires as also changes to laws could easily be communicated.
Laws and changes on taxes, made merchants and farmers have more trust since they were returned in the form of protection by Persian armies that had strict vigilance on the roads and also a coordinated system of intelligence to overwatch it
