[TF/P] _inulin at the end of the proximal tubule is 3 and at the same place [TF/P]_Na = 1. You conclude from this that

A) 2/3 of the Na is re-absorbed in the proximal tubule
B) 1/3 of the water is re-absorbed in the proxim al tubule
C) The fluid reabsorbed in the proximal tubule is isoosmolar with plasma
D) Inulin is freely filtered but not reabsorbed or secreted
E) Both A and C are true