已知{a_n}是等差数列，a₁=-9,S₃=S₇,那么使其前n项和S_n最小的n是（  ）

近几来，微信朋友圈文化改变着人们的社交方式,改变着人们与世界的连接状态。但是，随着微信用户数蒸蒸日上，根据可疑的养生秘籍、五花八门的商业广告充斥其间，让人不堪其扰。从文化的角度看，材料说明（     ）。

①文化影响人们的交往行为和交往方式

②政府要加强对文化市场的管理和引导

③大众传媒是文化传播的主要途径    

④科技是影响文化发展的重要因素

    We have a big playground in our school .We all like to 1 games 2 after school .It's Friday .We have only two classes 3 the afternoon . 4 school is over（结束的）,a lot of students go to the playground quickly.  The boys of Grade Two often 5 soccer. The girls like 6 them playing .Soccer is their favorite sport . Their teacher Mr Li also 7 football. Li Ming , Li Lei and Wei Fang are students of Grade One .They sometimes play 8 the students of Class Two. It’s half past five 9 . It's time 10dinner . My father is waiting for me at the school gate .