A) In other classes at the same university, students who both wrote their own notes and used the pre-printed instructor notes were among the highest- performing students on class exams.
Out of scope: our case is for students who either use own notes or use instructors not. Not both.

B) The exams were not written by the course instructor.
Out of scope: we are not bothered who wrote exams

C) Studies have shown that the physical act of note-taking aids in the recall of what is noted, even for those who never review the notes.
Correct: This gives alternative explanation. Group A students were neither motivated, nor had better notes. The act of note-taking helped.

D) The instructor's notes were written in language that was so florid and wordy as to make the points difficult for students to comprehend.
Strengthens Conclusion Part 1.

E) Students in the course were not allowed to refer to any notes, whether their own or the instructor's, while taking the course exams.
Out of scope. We are talking of why scores are high for group A. It doesn't matter if reference was allowed or not.