The answer is b. The royal family was buried at St. Denis.
Explanation
Option 1: The Pope was buried at St. Denis.
This option is incorrect. The Popes are traditionally buried in Rome, specifically in St. Peter's Basilica in Vatican City.
Option 2: The royal family was buried at St. Denis.
This option is correct. The Basilica of Saint-Denis, located in the northern suburbs of Paris, is the burial site of the French royal family. It has been the necropolis of French kings and queens since the 10th century, and many monarchs, including Louis XVI and Marie Antoinette, are interred there.
Option 3: The Abbot was buried at St. Denis.
While it is possible that some abbots of the Basilica of Saint-Denis were buried there, this option does not reflect the primary historical significance of the site as the burial place of the French royal family.