税收改革旨在为中产阶级提供救济。

The tax reforms are aimed at providing relief for the middle ___class.

这部纪录片描绘了上层阶级的生活方式。

The documentary portrays the lifestyle of the upper ___class.

社会流动性允许个人在不同阶级之间移动。

Social mobility allows individuals to move between ___classes.