The acid strength of the active methylene group in
$(a)$ $CH_3COCH_2COOC_2H_5$
$(b)$ $CH_3COCH_2COCH_3$
$(c)$ $C_2H_5OOCCH_2COOC_2H_5$
decreases as:

The product $(A)$ of the reaction is:

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

Compound $(B)$ is

If $(\pm)$ $2$-methylbutanoic acid is esterified by reaction with $(\pm)$ $2$-butanol,how many optically active compounds will be present in the final equilibrium reaction mixture?

$(i) \ F_3CCOOH$
$(ii) \ CH_3COOH$
$(iii) \ C_6H_5COOH$
$(iv) \ CH_3CH_2COOH$
Correct order of $pK_a$ value is: