5. What are the major species present at the indicated point in the titration of histidine?

a) dipositive form only
b) dipositive and monopositive forms
c) monopositive form only
d) monopositive and isoelectric forms
e) isoelectric form only
f) isoelectric and mononegative forms
g) mononegative form only
h) mononegative and dinegative forms
i) dinegative form only

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