According to the author, self-study

A．Teachers and students seldom meet each other in class of distance education.
B．Students can have their lessons in whatever order they like in distance education.
C．Students can study at their own pace in distance education.
D．It will take students a long time to get feedback of their assignments in distance education.

A．the length of the courses in distance education is shorter than that of college courses.
B．distance education only provides courses of low levels.
C．students need not spend a lot of money on getting a diploma in distance education.
D．students can enjoy a great variety of subjects provided by distance education.