Among the following sentences, which is employed by the author to refute the counter-argument above?

A. The notes may be available only to those students who take certain sections of a course and not others, thus giving some students an extra option.B. Students should be learning how to develop their own note-taking, organizing, and thinking skills rather than swallowing the material whole as neatly packaged and delivered.C. Skipping class may mean missed opportunities for students to ask questions or to participate in experiments or in group discussions, all of which often help clarify concepts under study.D. Not only do such businesses give certain students unfair advantages and discourage class attendance, but they also prohibit the development of students’ important learning skills, despite the services’ claims to the contrary.