Three colourless liquids P, Q and R are acetaldehyde, benzaldehyde and acetone in some order. P gives a red precipitate with Fehling solution and a yellow precipitate with $\mathrm{I}{}_2$/$\mathrm{NaOH}$. Q gives a silver mirror with Tollens reagent but no red precipitate with Fehling solution and no iodoform. R gives iodoform but does not reduce Tollens or Fehling reagent. P, Q and R are respectively

1. Aacetaldehyde, benzaldehyde, acetone
2. Bbenzaldehyde, acetaldehyde, acetone
3. Cacetone, benzaldehyde, acetaldehyde
4. Dacetaldehyde, acetone, benzaldehyde