A、In 1945. B、In 1949. C、In 1952. D、In 1954. C 1945年联合国应邀在美国建立总部，1952年完成。

New York City is the largest city in the United States. Unlike most American cities, which make up only a part of a particular county, New York City is made up of five separate counties, which are called boroughs. They are Manhattan, Queens, Brooklyn, Bronx and Staten Island.
    Manhattan, or New York County, is the smallest of the five boroughs, covering an area of 59.5 sq km (23 sq mi). It is the glittering heart of the metropolis. It is the site of virtually all of the hundreds of skyscrapers that are the symbol of the city. Among the more famous of these are the Empire State Building, the Chrysler Building, and Citicorp Center. The 110-story twin towers of the World Trade Center were also among New York’s famous skyscrapers until they were destroyed in a terrorist attack in 2001.
    Manhattan is the center of New York’s cultural life. Numerous stage and motion picture theaters are located around Broadway in Midtown, which includes Times Square. The borough is the home of prominent music and dance organizations, such as the New York City Opera Company, the Metropolitan Opera Association, American Bailer Theatre, and the New York City Ballet.
    In 1945, the United States Congress invited the United Nations to establish its permanent headquarters in the United States. Completed in 1952, the UN complex sits in Manhattan, alongside the East River, in the city of New York.