阅读理解。 The Forbidden City (Imperial Palace) in the heart of Beijing is the largest and most complete imperial palace and ancient building complex in China, and the world at large. Its construction began in 1406 and was completed 14 years later, having a history so far of more than 580 years. Twenty-four emperors from the Ming and Qing dynasties lived and ruled China from there. Most of the buildings in the Forbidden City were rebuilt many times, although they maintained the original architectural style. The Forbidden City, extending 753meters from east to west, and 961 meters from north to south makes a rectangular shape and covers a total area of 720,000 square meters. It consists of several dozen compounds of varying sizes and some 9,900 bays of rooms, with a total floor area of 150,000 square meters. Most of the buildings were built with wood, roofed with yellow glazed tiles(琉璃瓦)and built on blue-and-white stone foundations, looking solemn and brilliant. City walls are 10 meters high, and a 52-meter-wide moat(护城河) surrounds the Forbidden City. Three- storied towers are placed at each corner of the wall. The buildings of the Forbidden City fully embody the artistic features and style of ancient Chinese palace architecture, and can be called a masterpiece in Chinese, even the world, architectural history. Today, as the largest museum of cultural relics in China, the Forbidden City, also called the Palace Museum, collected and displayed about one million precious historical relics from the Shang dynasty (16th century B.C. - 11th century B. C. ) to the Qing dynasty. It was made part of the world cultural heritage list in 1987. 1. From the text we know that the shape of the Forbidden City is _____. A. B. C. D. 2. The underlined word 'maintained' in the first paragraph means _____. A. continued B. kept C. supported D. contained 3. The reason why the buildings of the Forbidden City can be called a masterpiece in Chinese architectural history is that _____. A. twenty-four emperors lived and ruled China there B. it has a history of more than 580 years C. it makes a rectangular shape and covers a total area of 720,000 square meters D. the buildings there fully embody the artistic features and style of ancient Chinese palace architecture 4. The earliest historical relics collected and displayed in the Palace Museum may have a history of _____. A. about 600 years B. over 580 years C. over 3,000 years D. nearly 100 years