The ancient civilization that developed an efficient postal system and network of roads was the Romans (option c). The Roman road system was a network of major highways that facilitated trade, military transport, and communication throughout the Roman Empire. The Romans also established a courier service known as the Cursus Publicus, which was responsible for delivering official communications, including government and military messages, across the empire. The service was efficient and reliable, with stations set up at regular intervals along the road network to ensure speedy delivery of messages.