A certain medication, although it works well in the lab, doesn't work well in the body because it doesn't dissolve well enough in the blood (which is mostly water). To make this medication more water soluble, adding which of the following is most likely to work?
A. Removal of amino groups
B. Removal of any functional group that can act as a base
C. Removal of a phosphate groups
D. Addition of CH3 groups
E. Addition of hydroxyl group