Why Do Changes in PH Interfere with the Function of Proteins

Why do changes in pH interfere with the function of proteins? For your answer, consider the acid/base character of many amino acid side chains.

A) At high pH the acidic side chains of amino acids such as glutamic acid and tyrosine will become negatively charged as they lose a hydrogen ion.
B) At low pH the alkaline side chains of amino acids such as lysine and histidine will become positively charged as they gain a hydrogen ion.
C) A change in pH can result in a change in the type of molecular attractions that occur among amino acids within a polypeptide.
D) all of the above