The poisonous gas 'Lewisite' is obtained by the reaction of:

Which one of the following carbonyl compounds cannot be prepared by addition of water on an alkyne in the presence of $HgSO_4$ and $H_2SO_4$?

Which series of reagents can be used to convert acetylene into higher alkynes?

In which of the following molecules,$2$ $\pi$ bonds are present?

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

Predict the correct intermediate and product in the following reaction: $CH_3-C \equiv CH \xrightarrow[HgSO_4]{H_2O, H_2SO_4} \text{Intermediate } (A) \to \text{Product } (B)$