It has created a group of second-class citizens. It's a source of social stratification, inequality and discrimination, and that is why many feel it should be removed.
它已经制造了一群二等公民，也是社会分层、失衡与歧视的根源，这是许多人认为它应该被取消的原因。
2
The combination of physics stratification teaching with the class teaching of "problem-research" could enhance the efficiency of physics teaching.
物理分层教学与“问题——研究”课堂教学模式的有机结合能有效地提高物理教学的效率。
3
In the study of social stratification, scholars focus more on the income of the middle class in large cities, education, social status and other aspects of differentiation.