某市用37辆汽车往灾区运送一批救灾物资，假设以v（km/h）的速度直达灾区，已知某市到灾区公路线长400km，为了安全起见，两辆汽车的间距不得小于${\left(\frac{v}{20}\right)}^2$km，那么这批物资全部到达灾区的最少时间是____h（车身长度不计）．

通读下面的短文，掌握其大意，然后从各题所给的A、B、C三个选项中选出一个最佳答案。

Dear Sally,

    How are you? I'm happy that you can do the things you 1 at home. I never have fun, because there are too many 2 in my family. My parents are strict. I have to  3 at six o'clock every morning. And I have to make my bedroom4 before breakfast and then go to school. I can't play with my friends after school. I have to do 5 homework. After dinner I have to take the dog for    6 walk in the park. I can't watch TV on school nights. I have to  7 the violin for an hour. I can't go to bed late. I have to be in bed 8 nine o'clock. On weekends I have to clean my room and 9 the dishes. I also have to go to learn the violin on Sundays. I'm 10  tired. Can you help me?

                                                                                                                                                                    Yours,  

                                                                                                                                                                      Lisa

下列属于社会经济地图的是（    ）

①地形图 ②气候图 ③水文图 ④矿产图 ⑤工业图

⑥商业图 ⑦农业图 ⑧交通图 ⑨人口分布图 ⑩植被图