Which of the following imaging modalities used in evaluating renal colic is the MOST sensitive and specific for identifying renal calculi or hydronephrosis?
(A) Ultrasonography.
(B) Kidneys, ureters, and bladder (KUB) plain radiograph.
(C) Helical CT without intravenous contrast.
(D) Intravenous pyelography (IVP).