How many moles of HCl need to be added to a 500 ml solution of 0.1 M leucine at pH 9.74 to precipitate the leucine from the solution? Assume addition of HCl does not change the volume of the solution.
A. 5 millimoles
B. 25 millimoles
C. 50 millimoles
D. 75 millimoles
E. Addition of HCI cannot change the solubility of leucine.