The correct answer is option 'D', Medieval period.

The Medieval period, also known as the Middle Ages, refers to the time period that lasted from the 5th to the 15th century. It was a time of significant social, political, and cultural change, characterized by feudalism, the rise of Christianity, and the decline of the Roman Empire.

Umberto Eco, an Italian novelist, philosopher, and literary critic, is well-known for his novels that are set in the Medieval period. His works often explore the intellectual and cultural climate of this era, combining historical events with fictional narratives.

Here are some of Umberto Eco's notable novels that deal with the Medieval period:

1. "The Name of the Rose": This is Eco's most famous novel, published in 1980. Set in the 14th century, it follows the Franciscan friar William of Baskerville as he investigates a series of mysterious deaths in an Italian monastery. The novel explores themes of religion, power, and knowledge, and is known for its detailed historical accuracy.

2. "Foucault's Pendulum": Published in 1988, this novel revolves around three editors who create a fictional conspiracy theory involving the Knights Templar, the Rosicrucians, and other secret societies. The story moves between the present day and various historical periods, including the Medieval era, as the characters become entangled in their own creation.

3. "Baudolino": Released in 2000, this novel tells the story of Baudolino, a young man from the 12th century who embarks on a series of adventures, including encounters with historical figures like Frederick Barbarossa and Prester John. The novel explores themes of truth, fiction, and the power of storytelling.

Overall, Umberto Eco's novels set in the Medieval period provide readers with a rich and immersive experience of this fascinating historical era. Through his meticulous research and storytelling skills, Eco brings to life the complex social, political, and cultural dynamics of the time, making his works both educational and entertaining for readers interested in this period of history.