2015年初，俄罗斯政府计划将无偿发放远东地区（乌拉尔山以东）的土地给俄罗斯公民，主要从事农业生产。该项政策的实施，将刺激其欧洲部分地区的人口向远东地区迁移。下图为1990～2010年俄罗斯远东地区人口资料。目前，影响俄罗斯远东地区人口迁入的主导因素和主要目的分别是（   ）

①乙型肝炎 ②淋病 ③梅毒 ④流感 ⑤艾滋病 ⑥疱疹 ⑦尖锐湿疣 ⑧系统性红斑狼疮

若3a^m﹣1bc²和﹣2a³b^n﹣2c²是同类项，则m+n=____ 

任务型阅读

    My name is George．I'm from England．Now I'm studying in Germany．I get to school at 7：30 every morning．I find many of my schoolmates come to school by bike．  ①   

    This is an interesting thing for me．In England people usually drive，take a bus or walk somewhere，for example，to school．In Germany, I often see people，even people over eighty years old going somewhere by bike．It makes me think：  ②   

My father gives the answer．We are living in Northern Germany．It is very flat(平坦的).So it is easy for people here to go somewhere quickly by bike .And it's cheaper than(比…….便宜)going by car or by bus．Also,it's good for the environment(环境)．

    I like riding bikes now．   ③    When I go back to England，I will ride more and ask my friends to ride with me．I think they will like tiding bikes，too．

根据材料内容完成下列任务。