对于不同的x，下列关于年龄的统计量不会发生改变的是（   ）

Ⅰ．取样、氧的固定

用溶解氧瓶采集水样，记录大气压及水体温度．将水样与Mn（OH）₂碱性悬浊液（含有KI）混合，反应生成MnO（OH）₂，实现氧的固定．

Ⅱ．酸化、滴定

在碘量瓶中将因氧后的水样酸化，MnO（OH）₂被I^﹣还原为Mn²⁺（该反应放热），在暗处静置5min，然后用标准Na₂S₂O₃溶液滴定生成的I₂（2S₂O ${}_3^{2-}$ +I₂═2I^﹣+S₄O ${}_6^{2-}$ ）

回答下列问题：

知识应用，解决问题．

（一）预习思考

材料一：据报道，2012年1月15日，广西龙江河拉浪水电站网箱养鱼出现死鱼现象被网络曝光，龙江河宜州拉浪码头前200米水质量金属超标80倍，龙江河段检测出重金属镉含量超标；据专家介绍，镉超标聚集会对人的肾脏带来影响，沿岸及下游居民饮水安全遭到严重威胁．

材料二：水是一切生命赖以生存、社会经济发展不可缺少和不可替代的重要自然资源和环境要素．在全球范围内，水质的污染、需水量的迅速增加以及部门间竞争性开发所导致的不合理利用，使水资源进一步短缺，水资源更加恶化，严重的影响了社会经济的发展，威胁着人类的福祉．

（二）设问解疑

    Believe it or not, school uniforms are absolutely not only clothes for students. They stand for the culture or beauty appreciation standard of a country. To wear uniforms has become a trend in most countries in modern society. Well, let's take a look at school uniforms in different nations. This will be interesting. And here, you will detect diverse allure (魅力)！

    The style of England school uniforms is rather classic, simple and respectable. Middle school students must wear traditional western-style school uniforms. Boys wear traditional western-style clothes, regular leather shoes and must wear neckties. Girls also wear western-style clothes, regular leather shoes and must wear bow ties. This classic clothing style unconsciously affects England students' temperament(性格)and also sense of beauty.

    Both boy and girl students in Australia are required to wear black leather shoes and white socks. They wear school uniforms all the time except the physical education, when they need to wear gym suits.

    Students in Malaysia obey rather strict rules. Girls' dresses must be long to cover the knees. Shirts must cover the elbow. Comparing with Thai students, they are much more conservative. School uniforms in most schools of China are only different in size. You can't find big differences between boys' uniforms and girls' uniforms only from the appearance. Both of them are loose sport suits.