Steve is performing a titration, where a base is at an unknown concentration. What

Steve is performing a titration, where a base is at an unknown concentration. What would he choose as his indicator solution? A. A chemical that clear when acidic and turns color when basic.
B. A chemical that's clear when basic and turns color when acidic.
C. A chemical that runs color when the temperature changes.
D. A chemical that buffers the solution.