Reaction: $CH_3-CO-CH_2-CH_2-CH_2-CH_2-CHO \xrightarrow{HO^{-}/\Delta} \underset{(73\%)}{(A)}$
Product $(A)$ is

The product $A$ in the above reaction is

In a set of the given reactions,acetic acid yielded a product $C$. Product $C$ would be:
$CH_3COOH + PCl_5 \to A$ $\xrightarrow{C_6H_6, \text{anh. } AlCl_3} B$ $\xrightarrow{C_2H_5MgBr, \text{ether}} C$

Reaction of iso-propylbenzene with $O_2$ followed by treatment with $H_3O^{+}$ forms phenol and a by-product $P$. Reaction of $P$ with $3$ equivalents of $Cl_2$ gives compound $Q$. Treatment of $Q$ with $Ca(OH)_2$ produces compound $R$ and calcium salt $S$. The correct statement(s) regarding $P, Q, R$ and $S$ is(are):
$(A)$ Reaction of $P$ with $R$ in the presence of $KOH$ gives chloritone.
$(B)$ Reaction of $R$ with $O_2$ in the presence of light gives phosgene gas.
$(C)$ $Q$ reacts with aqueous $NaOH$ to produce $Cl_3CCH_2OH$ and $Cl_3CCOONa$.
$(D)$ $S$ on heating gives $P$.

The products $(A)$ and $(B)$ respectively in the above reaction are:

Nucleophilic addition reaction will be most favoured in which among the following compounds?