Which of the following should be done to ensure patient safety before a contrasted radiographic study?

A. Ask the patient about previous hypersensitivity reactions to contrast media.
B. Verify that the dosage is appropriate for the patient's weight and age.
C. Obtain informed consent.
D. Observe the patient's skin color, tone and pitch of voice, and presence of apprehension, in order to better recognize changes from baseline.
E. All of the above are true.