The law covers four categories of experiments.

这一原理适用于4类试验。

《柯林斯英汉双解大词典》

Garbage sorting includes four categories—recyclable, harmful, dry and wet waste.

垃圾分类包括四种类别：可回收物、有害垃圾、干垃圾和湿垃圾。

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People in Shanghai know that garbage is sorted into four categories (类别): recyclable, harmful, dry and wet waste.

上海的居民知道垃圾分为四类：可回收垃圾、有害垃圾、干垃圾和湿垃圾。

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There are four categories of figure skating: men's singles,women's singles, pairs,and ice dancing.

VOA: special.2010.02.10

They define four credit risk categories and they define a formula involving the amount of assets in each of the categories.

他们定义了四个风险等级,然后根据每个风险等级下的资产额,定义了一个资产总额的计算公式

耶鲁公开课 - 金融市场课程节选

Caillois divides play into four categories: agon (competition), alea (chance), mimicry (simulation), and ilinx (vertigo).

NEWYORKER: Master of Play

The Northern League sent secret assessors to clubs and ranked them on four categories of ill-discipline.

BBC: Northern League publishes swearing league table

Facilitators boiled down the comments into five problem statements for each of the four categories.

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