单项选择题

The Pentagon(五角大楼)
The Pentagon, headquarters of the Department of Defence in US, is one of the world’s largest office buildings. It is twice the size of the Merchandise Mart in Chicago, and has three times the floor space of the Empire State Building in New York. There are very few people throughout the United States who do not have some knowledge of the Pentagon. Many have followed news stories emanating from the defence establishment housed in this building. However, relatively few people have had the opportunity to visit.
The Pentagon is virtually a city in itself. Approximately 23,000 employees, both military and civilian, contribute to the planning and execution of the defence of the country. These people arrive daily from Washington, D.C. and its suburbs over approx imately 30 miles of access highways, including express bus lanes and one of the newest subway systems in the country. They ride past 200 acres of lawn to park approximately 8,770 cars in 16 parking lots; climb 131 stairways or ride 19 escalators to reach offices that occupy 3,705 square feet. While in the building, they tell time by 4,200 clocks, drink from 691 water fountains, utilize 284 rest rooms, consume 4,500 cups of coffee, 1,700 pints of milk and 6,800 soft drinks prepared or served by a restaurant staff of 230 persons and distributed in 1 dining room, 2 cafeterias, 6 snack bars, and an outdoor snack bar. The restaurant service is a privately run civilian operation under contract to the Pentagon.
Stripped of its occupants, furniture and various decorations, the building alone in an extraordinary structure. Built during the early years of World War Ⅱ, it is still thought of as one of the most efficient office buildings in the world. Despite 17.5 miles of corridors it takes only seven minutes to walk between any two points in the building.
Which of the following statements about the structure of the Pentagon is true