The product is:

From the following reactions,identify the reactions that give carboxylic acids as products.

Arrange the following compounds in the increasing order of their $pK_a$ values:
$I.$ Phenol
$II.$ $p$-Nitrophenol
$III.$ Ethanol
$IV.$ $p$-Nitrobenzoic acid

An unknown compound $(A)$ (molar mass $= 180$) on acylation gives a product (molar mass $= 390$). Find the number of hydroxyl group present in compound $(A)$.

Match the reactions given in Column-$I$ with their names in Column-$II$.

Column-$I$ (Reaction)	Column-$II$ (Name)
$A$. $RCH_2COOH \rightarrow[H_2O]{X_2/P} RCH(X)COOH$	$i$. Decarboxylation
$B$. $RCOONa \rightarrow[NaOH, CaO, \Delta]{\text{soda lime}} RH$	$ii$. Grignard reaction
$C$. $RCOOH + R'OH \leftrightarrow{H^{+}} RCOOR' + H_2O$	$iii$. Hell-Volhard-Zelinsky reaction
$D$. $RMgX + R'CHO \rightarrow{H_3O^{+}} RCH(OH)R'$	$iv$. Esterification

What are $\underline{A}, \underline{B}, \underline{C}$ in the following reactions?
$(I)$ $(CH_3 CO_2)_2 Ca \stackrel{\Delta}{\longrightarrow} \underline{A}$
$(II)$ $CH_3 CO_2 H \underset{\text{Red P}}{\stackrel{HI}{\longrightarrow}} \underline{B}$
$(III)$ $2 CH_3 CO_2 H \stackrel{P_4 O_{10}}{\longrightarrow} \underline{C}$
$\underline{A} \quad \underline{B} \quad \underline{C}$