Buffer regions for polyprotic acid?

Question

How many buffer regions exist for a polyprotic acid?

a. One. There is only one buffer region no matter how many titratable protons there are in the acid.
b. one less than the number of acidic hydrogen ions
c. one more than the number of acidic hydrogen ions
d. one, but it is really, really large.
e. there is one buffer region for each of the titratable protons in the acid. It may be difficult to discern all of them from an experimental potentiometric titration curve, but they all exist.

Answer 1

e
pH1=pKa1+/-1
pH2=pKa2+/-1
pH3=pKa3+/-1