不同物质根据不同标准，如用途、状态、性质、组成、构成等，具有很多种分类依据。根据所学知识，自拟分类标准，对以下物质进行分类（填序号）：
①盐酸　　　②碳酸钠溶液　　　③水银　　　④黄铁矿　　　⑤硫酸　　⑥碘酒
分类标准____  ，共包括三种物质为 ____ 。

清朝有效地加强了中央对地方，特别是对边疆的管理与统治，其中我们可以借鉴的有
①尊重各民族自己的社会习俗和宗教信仰②重视边疆地区的交通建设和军事防卫
③对分裂势力进行坚决军事打击④大事集权，小事放权

同一平面内的三个力，大小分别为4 N、6 N、7 N，若三力同时作用于某一物体，则该物体所受三力合力的最大值和最小值分别为（　　）

短文改错。

例：Jim get up at seven in the morning.     Gets

    Different people like to do different things in their free time. Do you want to know what I do in my free time? I do lot ____ of things in my free time. First I like to listen to music. It make ____ me relaxed. but ____ happy. My favourite singer is Zhang Jie. I can sing most of his song____ . I aso like to watch TV. And I think watch ____ TV can help me learn a lot more outside class. Sometimes I go swimming and ____ my mother. She is good at swimming. I hope I can swim as better____  as you ____ someday. When I'm not busy, I also like to play the violin with my friends.it's quiteinterested____ .As you see, I have great funny ____ in my free time. What about your ？Free time Activities? Can you tell me?