Acetophenone,when reacted with a base,$C_2H_5ONa$,yields a stable compound which has the structure:

The principal product of the reaction between methyl butanoate and $2$ moles of $CH_3MgBr$ after hydrolysis is

Assertion : Aldol condensation can be catalysed both by acids and bases.
Reason : $\beta$-Hydroxyaldehydes or ketones readily undergo acid-catalysed dehydration.

Reagents to carry out the above conversion,$P$,$Q$,$R$ respectively are:

Among the following,the marked proton of which compound shows the lowest $pK_{a}$ value?

Contents of three bottles were found to react as follows:
$(i)$ Neither with Fehling's solution nor with Tollen's reagent
$(ii)$ Only with Tollen's reagent but not with Fehling's solution
$(iii)$ With both Tollen's reagent and Fehling's solution.
If they contained either ethanal,propanone,or benzaldehyde,which bottle contained which?