The simplest alkyne is represented by

Propyne reacts with excess $HBr$ to form the compound $Z$. The structure of $Z$ 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 $(B)$?

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

Identify the correct order of acidic strength for the following hydrocarbons:

The number of $\sigma$ and $\pi$ bonds present in $pent-4-en-1-yne$ is