Final answer:
The sea just to the east of Italy named for a once-flourishing port is the Adriatic Sea, which was historically significant for trade and cultural interactions in the Mediterranean region. The correct option is a.
Step-by-step explanation:
The sea to the east of Italy named after a once-flourishing port is the Adriatic Sea. The Adriatic Sea is well-known for being the home of Venice, a historic seaport and a major center for maritime trade.
This sea was crucial for trade throughout history, as it allowed for easy access to various Mediterranean regions and encouraged economic growth and cultural exchange.