There are three main classes of drugs, each of which has a different effect on the body.

主要有三大类的毒品，每一种对身体的影响不同。

There are two main classes of solids, crystalline and amorphous.

固体主要分为两类，结晶的和无定形的。

There were three main classes in Inca  society, the top-class being royalty.

印加社会分为三个主要阶层，最高阶层是皇室。

These are activities outside of the main classes, what we would call " extracurricular" activities.

这些是主要课程之外的活动，我们称之为“课外”活动。

Workers in various industry branches took over  as the main production class of this changing society.

各行各业的工人成为这个不断变化的社会的主要生产阶级。

You've got four main classes of connective tissue — proper, or the kind you'd find in your ligaments and supporting your skin, along with cartilage, bone, and blood.

你有四种主要的结缔组织——固有的，或者你在韧带中找到的支持你皮肤的那种，以及软骨，骨骼和血液。

And when Marx looked at industrial capitalism taking shape around him, he saw two main classes: the working class (or proletariat) and the capitalists (or the bourgeoisie).

当马克思看着他周围正在形成的工业资本主义时，他看到了两个主要阶级：工人阶级（或无产阶级）和资本家（或资产阶级）。