阅读下列短文,从每题所给的四个选项(A、B、C和D)中,选出最佳选项。
Philadelphia, Pennsylvania is America's fifth largest city. Once a major American colonial city, it is the home of America's first library, its first hospital, and its first zoo. Now it is also the first US city to be named a World Heritage City. On November 6, 2015, Philadelphia joined more than 260 other cities that have been recognized for their influence on the world. These cities include Paris, France, Florence, Italy, and Cairo, Egypt.
The exciting news was announced by Philadelphia Mayor Michael Nutter, Deputy Mayor Alan Greenberger, responsible for economic development and business guidance, and the Global Philadelphia Association. "Today marks the start of a new and exciting chapter in the history of Philadelphia," remarked Nutter when the announcement was made. "As a World Heritage City, Philadelphia is being officially recognized on the global stage for its wealth of contributions to the world."
To be named a World Heritage City, a city must be home to a UNESCO World Heritage site. UNESCO World Heritage sites are selected for their universal value and significance. For Philadelphia, the site is Independence Hall.
Independence Hall is where two of the most important documents in US history — the Declaration of Independence and the US Constitution — were adopted. The Declaration of Independence, approved on July 4, 1776, united the 13 former British colonies and declared them independent from British rule. From then on, a democratic and free country was born, which changed the course of world history. The US Constitution, signed in 1787, established the American democratic system of government. A democracy is a system of government in which the people elect their leaders. The Constitution later spelled out the basic freedoms American citizens have.
Greenberger says the city's selection as a World Heritage City also reflects its educational, cultural, and economic achievements. The city is home to dozens of colleges and universities, and many museums, such as the Philadelphia Museum of Art. "Philadelphia has rightfully earned its place as one of the greatest cities in the world. As we celebrate this milestone, we will focus even more on improving Philadelphia's status as a World Heritage City to attract more guests to visit, invest, work, study and live here." Greenberger says.