The Activity of Lysozyme Is Greater Than 50% of Maximum

The activity of lysozyme is greater than 50% of maximum between pH 3.8 and 6.1 with peak activity occurring around pH 5. Below 3.8 and above 6.1, the activity drops rapidly. Which of the following provides the best explanation for this?

A) two histidine residues in the active site must be protonated for enzyme activity
B) the active site contains an aspartic acid and glutamic acid, both of which must be deprotonated
C) the active site contains an aspartic acid that must be deprotonated and a glutamic acid that must be protonated
D) the active site contains a histidine that must be protonated and a glutamic acid that must be deprotonated
E) none of the above