The above conversion can be achieved by:

Compound $(A)$,$C_6H_{12}O_3$,when treated with $I_2$ in aqueous sodium hydroxide gives a yellow precipitate. When $(A)$ is treated with Tollens' reagent,no reaction occurs. When $(A)$ is hydrolysed and then treated with Tollens' reagent,a silver mirror is formed in the test tube. Compound $(A)$ will be

Product $(D)$ in the above sequence is:

Which of the following reagents can be used for the given chemical transformation?

$A$ mixture of benzaldehyde and formaldehyde on heating with aqueous $NaOH$ solution gives :-

Complete reaction of acetaldehyde with excess formaldehyde,upon heating with conc. $NaOH$ solution,gives $P$ and $Q$. Compound $P$ does not give Tollens' test,whereas $Q$ on acidification gives positive Tollens' test. Treatment of $P$ with excess cyclohexanone in the presence of catalytic amount of $p$-toluenesulfonic acid $(PTSA)$ gives product $R$. Sum of the number of methylene groups $(-CH_2-)$ and oxygen atoms in $R$ is....