The main purpose of this passage is to tell us ______.

A．smaller class brings lower achievements of the students
B．special attention encourages the students to do better in class
C．single sex is the only factor that influences the students' behaviors
D．single sex helps the students learn more in class

A．some researches suggest that boys and girls do not study in the same way
B．they are inspired by the success of Young Women's Leadership School
C．researches in single-sex class prove that it works better for education
D．problems in coeducation show that a single-sex school might be a better choice