EVERY few hundred years, a sleeping giant in southern Italy awakens with a bang, spewing volcanic ash across the countryside. The volcano, called Mount Vesuvius, formed 25,000 years ago. During its most explosive eruptions, the volcano could blanket nearby cities with hot ash, sometimes also burying them with deadly flows of mud and rocks. One famous eruption occurred nearly 2,000 years ago, in the year AD 79. It lasted 18 hours and destroyed the Roman cities of Pompeii and Herculaneum, killing thousands of people as they tried to escape. Scientists and city officials had supposed that Naples, one of Italy's most populous cities, was far enough away that it would be safe from the volcano's _ . New evidence suggests that this might not be the case. Researchers recently discovered 4000-year-old layers of ash and mud under present-day Naples. Just outside the city, they also uncovered abandoned villages, as well as human and animal skeletons. Most surprising of all, the researchers say, was the discovery of thousands of footprints from the same time period, pressed into layers of wet ash that had rained from the sky. The footprints show that thousands of people were fleeing to the northwest, away from the volcano, as it erupted. Mount Vesuvius hasn't had a major eruption since 1631, but it's still very active. The discovery of the ancient ash layers, skeletons, and footprints is a warning that modern Naples, a city of 3 million people, isn't safe from the volcano, scientists say. So, when the volcano begins to rumble again, Naples should have an emergency evacuation plan ready - just in case. What can we conclude from the passage?
City Pompeii has been rebuilt now. City Naples isn't suitable for living. Mount Vesuvius will not erupt in a hundred years. Mount Vesuvius is a potential danger to Naples.