The trend in acidic behaviour of the following hydrocarbons is:
$a: HC \equiv CH$
$b: CH_2 = CH_2$
$c: CH_3 - CH_3$
$d: CH_3 - C \equiv CH$

Acetylene reacts with a $42\% H_2SO_4$ solution containing $1\% HgSO_4$ to give

Compound $(X)$ [styrene] is subjected to the following sequence of reactions: $(i)$ $Br_2/CHCl_3$, $(ii)$ $NaNH_2$ (excess), $(iii)$ $CH_3I$, $(iv)$ $H_2, Na/NH_3(l)$, giving Major Product $(Y)$. The molar mass of the major product $(Y)$ formed is . . . . . . $\text{g mol}^{-1}$. (Given molar mass in $\text{g mol}^{-1}$: $C:12, H:1$)

$(A)$ $\xrightarrow[dil. H_2SO_4]{HgSO_4} (B)$ $\xrightarrow{LiAlH_4} \underset{\text{racemic mixture}}{(C)}$
$\therefore$ reactant $(A)$ is

The major product in the following reaction is

An inorganic metal oxide $(A)$ heated with carbon gives compound $(B)$,which on reaction with water gives ethyne. What are the compounds $(A)$ and $(B)$?