Starting from the Collecting Duct, Indicate the Order in Which

Multiple Choice

Starting from the collecting duct, indicate the order in which urea molecules move to maintain the medullary concentration gradient.
(1) Ascending limb
(2) Distal convoluted tubule
(3) Interstitial fluid
(4) Collecting duct
(5) Descending limb

A) 2, 5, 1, 4, 3
B) 1, 3, 5, 2, 4
C) 3, 5, 1, 2, 4
D) 4, 2, 1, 3, 5
E) 4, 3, 5, 1, 2