In the Following Titration Curve,what Does the Inflection Point Represent

In the following titration curve,what does the inflection point represent?

A) pH of solution equals pK_a of weak acid
B) concentration of weak acid and conjugate base are equal
C) the pH where the solution would function most effectively as a buffer
D) the weak acid is 50% protonated,50% deprotonated
E) all of the above