Explanation: Think of the areas which are described. In a city, people are usually packed in tight areas, such as apartment buildings. Cities usually have the highest population as well. In suburban areas(neighborhoods) there are still a big population but, they are more spaced out. In rural areas(farms, small towns) there are less people. Because of this, they are more spread out.
"<span>the assassination of Archduke Franz Ferdinand" is thought to be the spark that lit the powder-keg </span>of war at the beginning of the 20th century. A dense web of alliances was set off from this shooting.