所有四边形的内角和有时是360°，有时是540°．       ．

清政府规定：“凡通商口岸，内省腹地，其应兴铁路、轮船、开矿、种植、纺织、制造之外，一体准民间开设，无所禁止，或集股，或自办，悉听其便。全以商贾之道行之，绝不拘于官场体统。”该政策（    ）

阅读理解

    My name is Sun Liang．Li Feng is my cousin．He is thirteen years old and I'm twelve years old．We study in the same school but not in the same grade．He is in Grade 8 and I'm in Grade 7．

    Li Feng is tall and strong．He plays basketball well．He thinks it's a good way to stay healthy．So he often plays basketball with his classmates in the playground．He likes collecting the pictures of famous basketball players．Last Sunday,he watched a basketball match．He was happy because he saw his favourite basketball star．

    I also like playing sports but music is my favourite．I think it's a good way to relax after a busy day．My father is a music teacher and he is good at playing the piano．So I learn from him to play the piano．It was my birthday yesterday．I had a party and I was happy．

根据材料内容选择最佳答案。

某校的校园内有一个由两个相同的正六边形（边长为2.5m）围成的花坛，如图中的阴影部分所示，校方先要将这个花坛在原有的基础上扩建成一个菱形区域如图所示，并在新扩充的部分种上草坪，则扩建后菱形区域的周长为（　　）