Final answer:
To choose the right indicator for an acid-base titration, you should consider the pH range at which the indicator changes color. In this case, phenolphthalein should be used because its color change occurs in the pH range of 8.2 to 10.
Step-by-step explanation:
When choosing the right indicator for an acid-base titration, you need to consider the pH range at which the indicator changes color. In this case, the unknown acid has a Ka value of 0.01, which indicates that it is a weak acid. For weak acids, the pH at the equivalence point is typically above 7. Therefore, phenolphthalein should be used as the indicator because its color change occurs in the pH range of 8.2 to 10.