What Is an Advantage of Using a Clear Mask When

What is an advantage of using a clear mask when administering oxygen to a patient?

A) If a film forms on the mask, then the oxygen in the tank has been "oxidized" and the tank must be changed.
B) It makes it easier to determine if the oxygen flow has diminished.
C) It can be determined if the patient has begun to breathe on their own because the "fogging" of the mask is easily visible.
D) The patient can easily communicate with the dental staff.