My holiday is coming.Yesterday I asked my American friends about the best way to travel around the United States. They said it was best to travel by 1 and gave me the 2.

    To fly, of course, is the fastest way, but one can't see anything during a 3 except the blue sky and white clouds. So it is not very interesting for one who wants to see the 4.Besides, the plane ticket is very 5.

    To travel by train is 6, because passengers can walk and buy food and drinks on a train. They can also see cities and the country through the windows. But trains don't leave or 7 at a place every day, and don't go to many cities.

    To travel by bus is easy, cheap and convenient, though not so fast as travelling by plane or so 8 as by train. You can find buses almost in every city. That makes travel arrangement easy.

    I take their 9.Now I have decided to go on an interesting 10 by bus to the east coast.

设直线l与球O有且只有一个公共点P，从直线l出发的两个半平面α，β截球O的两个截面圆的半径分别为1和$\sqrt{3}$，二面角α﹣l﹣β的平面角为$\frac{\mathrm{\pi }}{2}$，则球O的表面积为____ ．

野老歌

张籍

老农家贫在山住，耕种山田三四亩。苗疏税多不得食，输入官仓化为土。

岁暮锄犁傍空室，呼儿登山收橡实。西江贾客珠百斛，船中养犬长食肉。