还是among between

主语+vary between……and ，表示：在……和……之间，（主语）是不同或不等（变化）。
1. 如果vary后面接的是 A and B, A, B and C 之类含有连词 and 的词组，原则上应用 between 。
Class numbers vary between 25 and 30.
班级的数目从25到30不等。《牛津高阶英汉双解词典》

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Attitudes vary between individuals, societies, and cultures.
各个人、各个社会和各种文化之间的态度都不一样。（摘自《麦克米伦高阶英汉双解词典》）
Her feelings varied between joy and fear as she watched him fight. 当她观看他拳击的时候，时而喜悦，时而担心。

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The hopes,goals,fears and desiresvary widely between men and women,between the rich and the poor.
男人和女人之间，富人和穷人之间，希望、目标、恐惧和愿望都有很大的不同。2000.1四级
Beam heights vary between 500 and 600 mm, and widths vary between 200 and 250 mm.
光线（波）的高度在500到600毫米之间变化，宽度在200到250毫米之间变化。
Academic collaboration rates and citation associations vary substantially between countries and fields.
不同国家或领域之间学术合作率和论文交流差异很大。

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The data varies between 16 % and more than 20 %.
数据在百分之16-百分之20之间波动。
Does farm worker health vary between localised and globalised food supply systems?
在本地化和全球化的食品供应系统中，农场工人的健康状况是否有所不同？
2.如果vary后面接的是一个复数名词，按理说应该用 among ，但事实上也经常用介词 between（表示“每两者之间”）。如：
Average IQ scores tend to vary between countries.
各国的平均智商差距日趋扩大。
Salary scales vary between states / from state to state / according to state / with each state. 工资高低各州 / 一个州与另一州 / 视所在的州 / 各个州不同。（《《剑桥国际英语词典》》）
Services offered vary among the main high street banks. 各大商业银行提供的服务不尽相同。（《牛津英语搭配词典》）
Diet varies between different countries in the world.
世界上不同的国家其饮食是不同的。
The proportion of single parent families varies between different income groups.
单亲家庭比例在不同收入群中各不相同。《牛津高阶英汉双解词典》
Causes of suicide vary between different people, reports the People's Daily.
【还是among between】《人民日报》报道称，不同人群自杀的原因不尽相同。