The treatment of $CH_3MgX$ with $CH_3-C \equiv CH$ produces

Which alkyne yields butanoic acid $(CH_3CH_2CH_2CO_2H)$ as the only organic product on treatment with ozone followed by the hydrolysis?

Identify $A$ in the following reaction.
$A$ $\xrightarrow{\text{Lithium amide}} \text{Ethynyl lithium}$ $\xrightarrow{\text{Bromoethane}} \text{but-}1\text{-yne}$

$CH_3-C \equiv CH \xrightarrow[(ii) H_2O_2/OH^{\Theta}]{(i) BH_3-THF} (P)$
$CH_3-C \equiv CH \xrightarrow[(ii) NaBH_4]{(i) Hg(OAc)_2/H_2O} (Q)$
Choose the correct option

The shortest $C-C$ bond length is present in:

Number of $\sigma$ and $\pi$ bonds present in $but-1-ene-3-yne$ respectively are