all the classes
class：
1 a period when students meet to be taught a particular subject 在一个特定时间内对一班学生授教特定学科的一种课堂。一堂课。
2 a series of classes on a particular subject 授教一种特定学科的一系列课程。课程。
all the courses
course:
1 a series of lessons or lectures on a particular subject 有关某学科的系列课程，讲座。
2 a period of study at a college or university that leads to an exam or a qualification 大学中要进行考试或取得资格的课程。
all the lessons
lesson:
1 a period of time in which sb is taught sth 某人在一个特定时间内听授的课。一节课；一课时。
2 something that is intended to be learned 既定的教育课程。课；教学单元课。
all the subjects
subject:
an area of knowledge studied in a school, college, etc.在学校，大学等地方学习的某一领域的知识。学科；科目；课程。
