When an Acetic Acid Solution Is Titrated with Sodium Hydroxide

When an acetic acid solution is titrated with sodium hydroxide, the slope of the titration curve (pH versus volume of NaOH added) increases when sodium hydroxide is first added. This change shows that ________

A) nothing is happening during this part of the titration.
B) the reaction is very slow during this part of the titration.
C) a more concentrated solution of NaOH needs to be present to initiate the reaction.
D) acetic acid is being converted to sodium acetate.
E) the pH is not affected until all the acetic acid is consumed.