The \[p{{K}_{4}}\] values for the three ionizable groups X, Y and Z of glutamic acid are 4.3, 9.7 and 2.2 respectively \[\underset{X}{\mathop{H{{O}_{2}}C}}\,-C{{H}_{2}}-\underset{Y}{\mathop{\underset{_{+}N{{H}_{3}}}{\mathop{\underset{|}{\mathop{C}}\,}}\,H}}\,-\underset{Z}{\mathop{C{{O}_{2}}H}}\,\] The isoelectric point for the amino acid is:

• A. 7.00                 
• B. 3.25  
• C. 4.95                 
• D. 5.95