Compound $\mathrm{A}\left(\mathrm{C}_9 \mathrm{H}_{10} \mathrm{O}\right)$ shows positive iodoform test. Oxidation of A with $\mathrm{KMnO}_4 / \mathrm{KOH}$ gives acid $\mathrm{B}\left(\mathrm{C}_8 \mathrm{H}_6 \mathrm{O}_4\right)$. Anhydride of B is used for the preparation of phenolphthalein. Compound A is:
