69. In the titration of a weak acid HA with 0.100 M NaOH, the stoichiometric point is known to occur at a pH value of approximately 11. Which of the following indicators would be best to use to mark the endpoint of thus titration? (A) an indicator with Ka = 10-10 (B) an indicator with Ka = 10-8 (C) an indicator with Ka = 10-14 (D) an indicator with Ka = 10-11 (E) an indicator with Ka = 10-12