“齐国君王齐桓公，任用丞相叫管仲，‘尊王攘夷’为口号，第一霸主逞威风”。该歌谣所反映的历史时期是（    ）

    The United States is full of automobiles (机动车). There are still many families without cars. But some families have two or1more cars. However, cars are used for more than pleasure. They are a2part of life.

    Cars are used for3. They are driven to offices and factories by workers who have no other way to4their jobs. When salesmen are sent to different parts of the city, they have to drive in order to carry their products. Farmers have to drive into the city in order to shop for necessities.

    Sometimes, small children must be driven to5. In some cities, school buses are used only when children6__more than a mile from the school. One7drives on Mondays, taking her children and the neighbors' children as well. Another mother drives on Tuesdays, another on Wednesdays and so on. This is called forming a car pool (拼车). Working people also form car pools, with three or four people taking turns driving to the place8they work.

    More car pools should be formed in order to put9cars on the road and to use less oil.

    10 is a great problem, and so is the traffic in and around cities. Too many cars are being driven. Something should be done about the use of cars.

近代化包括政治的民主化、法制化，经济的市场化、工业化，社会生活的文明化、西方化，思想文化的科学化、民主化。世界各国在走向近代化过程中呈现出多样性的特点，俄国走上近代化的途径是

在$\frac{1}{x}$,$\frac{1}{2}$,$\frac{x^2+1}{2}$,$\frac{3xy}{\mathrm{\pi }}$,$\frac{3}{x+y}$,a+$\frac{1}{m}$中，分式的个数是（　　）