Read the selection and answer the question.
The Colosseum
Imagine being in Rome 1900 years ago. Huge crowds of people hurry down the street toward you, filled with excitement. They are going to see a battle of gladiators at the Colosseum, and the show is about to begin.
Gladiator battles were among the many spectacles that took place in Rome's Colosseum. The structure was a large oval similar to baseball and football stadiums of today. This remarkable arena was built almost 2000 years ago and was used for almost four centuries.
Construction of the Colosseum began in 72 A. D. during the rule of the Roman Emperor Vespasian. It was completed eight years later by Vespasian's son, Titus. The Flavian Amphitheater, as it was first called, stood 157 feet high. It was 620 feet long and 513 feet across. There were 80 entrances around the base: 76 for spectators, two for participants in the games, and two just for the emperor and his family. As in modern sports arenas, there were different seating levels. The ringside box seats were reserved for important officials. Lower level seats cost more than the upper level seats. Historians believe that the Colosseum could hold 45,000 people. (That's bigger than Boston's Fenway Park, which holds 34,000 Red Sox fans.) It even had a system for drawing a large awning over the seating area to protect spectators from the hot sun.
The inside oval was 287 feet long and 180 feet wide, making it about the size of a modern-day football field. It was the largest arena space in the world at that time. This area was built of wood and covered with sand. Beneath it lay a maze of hallways, rooms, and holding pens that held all of the elaborate decorations and props used in the shows. This arena space could also be flooded with water in order to stage battles with boats!
Spectators at the Colosseum often saw violent, bloody shows, and some events lasted all day. Sometimes men hunted wild animals, such as lions and tigers. Duels between gladiators began early in the day with wooden weapons. Battles to the death took place later in the day.
Then in 312 A. D., Constantine I became the first Christian emperor of Rome. Under his rule, the shows at the Colosseum became less violent. People began to question whether it was right to hunt animals and hold battles for entertainment.
The last known event in the great arena took place in 404 A. D. By that time, the Roman Empire was falling apart and excited crowds no longer filled the stadium. The Colosseum has stood at the center of the city through many centuries since then and can still be seen today.
Most of the information in this selection is organized by—

A
chronological order.

B
comparison/contrast.

C
problem and solution.

D
cause and effect.