Which of the following patients with nephrolithiasis can be safely discharged home?
(A) A 50-year-old diabetic man with associated urinary tract infection and signs of obstruction.
(B) A 30-year-old man with a single kidney and signs of obstruction.
(C) A 40-year-old man with a 4-mm stone in the distal ureter.
(D) A 25-year-old woman with uncontrolled pain and persistent vomiting.