Hutong is a kind of ancient typical city 5lrccl in Beijing.____ (surround) the Forbidden City, many were built during the Yuan, Ming and Qing ____ (dynasty). In order to establish the strongest power for emperors, the royal family planned the city and arranged the residential areas (住宅区). The Forbidden City- ____ center of the Beijing city, was the royal palace.

    At the end of the Qing dynasty, after ____ (close) China came under the influence from abroad, many old hutongs lost____ (they) former neat (灵巧的) arrangement.

    After the founding of the People's Republic of China in 1949, the conditions of hutong ____ (improve). But in recent years, the houses in many hutongs have been pulled ____ and then replaced by modem buildings. And the hutong today is fading into the shade for both tourists____ local people.

    However, in the urban district of Beijing, hutongs still occupy one ____ (three) of the total area, providing housing for half population, so many hutongs ____ (survive) these years. In this respect, we see Beijing as an ancient yet modem city.

嗟夫！予尝求古仁人之心，或异二者之为，何哉？不以物喜，不以己悲；居庙堂之高则忧其民；处江湖之远则忧其君。是进亦忧，退亦忧。然则何时而乐耶？其必曰“先天下之忧而忧，后天下之乐而乐”乎。噫！微斯人，吾谁与归？

对本文写作目的解说有误的一项是（    ）

关于动量守恒的条件，正确是（   ）