What Is the Purpose of Ionic Groups in the Active

What is the purpose of ionic groups in the active sites of enzymes? ​

A) to alter the substrate in a way that favors catalysis
B) to catalyze an acid/base reaction required for synthesis
C) to promote the binding of substrates that otherwise would not fit
D) to generate an electronic current to provide the energy for the reaction
E) to increase the salt concentration required for the chemical reaction to occur