Which of the following reacts with acetylene to form the war gas Lewisite?

Propyne on reaction with water in the presence of $40\% \ \text{H}_2\text{SO}_4$ and $1\% \ \text{HgSO}_4$ forms:

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

The compound $C_3H_4$ has a triple bond,which is indicated by its reaction with

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

In the reaction $HC \equiv CH + 2AgNO_3 \xrightarrow{NH_4OH} X + 2NH_4NO_3 + 2H_2O$,'$X$' is: