For Which Older Patient Should the Nurse Suspect a Decline

For which older patient should the nurse suspect a decline in the responsiveness of the immune system?

A) 78-year-old patient with pneumonia and temperature of 99.5°F
B) 68-year-old patient with a red itchy rash from contact with poison ivy
C) 80-year-old patient with swelling and redness around an abdominal incision
D) 66-year-old patient with 8 mm induration from a mumps skin test 72 hours earlier