In a classroom system, the students produce an output of information on tests and homework. This information becomes an input for the grading part of the system. Which statement about the output of the students is true?
A. The output of the students is not a part of the classroom system as a whole.
B. The output of students has the form of energy.
C. The output of the students can change the classroom system as a whole.
D. The output of the students does not affect the classroom system as a whole.