The word it in paragraph 2 refers to _______.

Câu hỏi: Read the following passage and mark the letter A, B, C or D on the answer sheet to indicate the correct answer to each of the questions.
Landscape architecture is the design and development of land for human use and enjoyment. Before the middle of the nineteenth century, landscape architecture was practiced as an art but not as a profession. Since ancient times, the art had been employed only by the wealthy, Romans had their courtyards, Persians their gardens, Italians their city plazas, and the French their palace grounds. The upper classes in the American colonies adopted the landscape style of the British, especially their elaborate gardens. As most landscape projects included gardens, the designers were called landscape gardeners.
The inventor of the term landscape architecture was a British scholar, Gilbert Laing Meason, who wrote it in a book in 1828. In the United States, the label was adopted by Frederick Law Olmstead, the first person to claim that title as his profession. Olmstead revolutionised the field when he and architect Calvert Vaux entered a competition for the design of New York's proposed Central Park. In 1858, Olmstead and Vaux's design was selected and it was built over the next 15 years.
Olmstead's concept was to make the park a symbol of democracy and egalitarian ideals. He saw it as a place that welcomed all classes of people and encouraged them to contemplate and recreate away from the pressures of everyday life. His novel design idea was to create what he called separate circulation systems" for the different classes of users - pedestrians, horseback riders, and horse-drawn carriages. Traffic moving through the park was concealed in sunken roadways hidden by shrubs to preserve the appearance of an unspoiled landscape. Today the park includes running tracks, ice skating rinks, a wildlife sanctuary, baseball fields. playgrounds, and a world-famous restaurant, Tavern on the Green.
Olmstend also designed the grounds of the United States Capitol building in Washington, D.C. he installed the marble terraces that project from the sides of the building. Some visitors to the Capital complained that they had no place to water their horses. In response, Olmstead designed an open-air brick building, the Summer House, which had a fountain from which horses could drink.
Landscape architects founded their own organisation in 1899, the American Society of Landscape Architects. A landscape architect must be familiar with mathematics, science, engineering, art, and technology. He must also understand the social context of the work and must be adept at dealing with politicians, public interest groups, and government agencies.
The profession has become increasingly specialized. Landscape designers and technicians or engineers plan and build the project. Landscape managers are concerned with the long-term care of the landscape. Landscape scientists work with the architects on technical problems in areas such as soils, hydrology. or botany. Public policy and planning strategies are developed with the aid of landscape planners. Garden designers work on private gardens as well as historic-garden preservation.
The word it in paragraph 2 refers to _______.
A. Olmstead and Vaux's design
B. the city
C. a large rectangular space
D. a public park