Final answer:
Trade flourished in the Roman Empire due to the empire's control over sea routes and an extensive network of roads (option b), which enabled efficient and less expensive transport of goods across the region.
Step-by-step explanation:
Trade in the Roman Empire was significantly aided by the empire's control of sea routes and the construction of an extensive network of good roads. This infrastructure facilitated the movement of goods, with sea shipping being considerably less expensive than land transport. Italy, as a central trade hub, benefitted from several fine seaports, such as Rome's port at Ostia, and both practical and luxury goods circulated around the Mediterranean facilitated by these trade networks.
Furthermore, long-distance trade, exemplified by the Silk Road, involved interconnected routes spanning from the Near East to the Far East, allowing for the exchange of various goods, including silk and Roman glassware. Romans capitalized on regional opportunities and directed skilled artisans to produce trade goods, lifting the economy. The extensive and strategic trade routes also allowed for the spread of cultural and intellectual innovations across the empire and beyond.