The test to differentiate between pentan-2-one and pentan-3-one is

An organic compound $$X$$ on treatment with PCC in dichloromethane gives the compound $$Y$$. Compound $$Y$$ reacts with $$\mathrm{I}_2$$ and alkali to form yellow precipitate of triiodomethane. The compound $$X$$ is

$$A, B$$ and $$C$$ respectively are

$$\begin{aligned} & \mathrm{CH}_3 \mathrm{CHO} \xrightarrow[\text { (ii) } \mathrm{H}_3 \mathrm{O}^{+}]{\text {(i) } \mathrm{CH}_3 \mathrm{MgBr}} A \xrightarrow[\Delta]{\text { Conc. } \mathrm{H}_2 \mathrm{SO}_4} \\ & B \xrightarrow[\text { (ii) } \mathrm{H}_2 \mathrm{O}, \mathrm{OH}^{-}]{\text {(i) } \mathrm{B}_2 \mathrm{H}_6} C \\ & \end{aligned}$$

$$A$$ and $$C$$ are