The most suitable indicator in acid-base titrations for weak acid and strong base is

Phenolphthalein changes color in the pH range of 8-10, which matches where weak acid and strong base titrations reach their endpoint. This indicator is colorless in acid and turns pink in base.

When a weak acid reacts with a strong base, the equivalence point occurs in the basic pH range above 7. Phenolphthalein’s color change happens exactly in this range.

Other indicators change color at different pH values that do not match this titration type. Phenolphthalein gives the most accurate endpoint detection for weak acid-strong base combinations.