A patient is scheduled for diagnostic testing. Which medication should the nurse anticipate that the health-care provider would order?

A. Barium sulfate is used as a contrast agent in radiographic diagnostic testing, particularly for imaging the gastrointestinal tract. B. Penicillin (PCN) is an antibiotic used to treat infections, not for diagnostic purposes. C. Estrogen is a hormone used in hormone replacement therapy and other treatments, not for diagnostic testing. D. Naloxone is used to reverse opioid overdose, not for diagnostic testing.