The end product of the following sequence is
$CaC_2$ $\xrightarrow{H_2O} B$ $\xrightarrow[HgSO_4]{H_2O, H_2SO_4} C$

Identify the alkyne formed by the reaction of calcium carbide with water.

What is the major organic product of the following reaction?
$Ph-C \equiv CH \xrightarrow[H_2SO_4]{Hg^{2+}, H_2O} ?$

$A$ metallic carbide on treatment with water gives a colourless gas which burns readily in air and which gives a precipitate with ammoniacal silver nitrate solution. The gas evolved is:

$HC \equiv CH$ $\xrightarrow[{excess}]{{CH_3MgBr}} \mathop {(A)}\limits_{\text{salt}} + \mathop {(B)}\limits_{\text{hydrocarbon}}$
$(A)$ $\xrightarrow[{excess}]{{CH_3I}} (C)$ $\xrightarrow[{(ii) H^{+} }]{{(i) NaNH_2}} (D)$

In the reaction sequence $CaC_2$ $\xrightarrow{H_2O} A$ $\xrightarrow[dil. H_2SO_4]{Hg^{+2}} B$ $\xrightarrow{Ni} H_2 C$,the product $C$ is: